Abstract:
The present invention relates to tools and system designs for chemical vapor deposition (CVD) systems and CVD synthesis used to deposit one or more thin film layers onto a flexible substrate or to grow nano-structured materials on large area flexible substrates and, more particularly, to scalable CVD coating and nanostructure manufacturing including CVD thin films and nano-structured materials such as nanotubes, nanowires and nanosheets.

Description:
This application claims the benefit of U.S. Provisional Application No. 62/012,178, filed on Jun. 13, 2014. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to substrate remounting and system designs for chemical vapor deposition (CVD) systems and CVD synthesis used to synthesize at least one layer or to grow at least one nano-structured material on at least one surface of a flexible substrate, and more particularly, to scalable thin film coating and nano-structured material manufacturing of products such as nanotubes, nanowires, and nanosheets. 
     Those skilled in the art will recognize that there is an ongoing interest in economical solutions that enable the manufacturing in large volume of higher quality, nano-structured materials (e.g., in tube, fiber or wire format, such as 1-5 mm tall, 10-20 nm thick vertically aligned carbon nanotubes; 100-200 nm thick vertically aligned carbon nanofibers; 10-50 μm long, 50-100 nm thick random or vertically aligned silicon nanowires as can be synthesized by CVD processes on, for example, flexible stainless steel foil). 
     It will be recognized that the ability to produce higher quantities of higher quality nano-structured materials at lower production cost per usable coated area is desirable, for example, to unlock many of the potential benefits that nano-structured material and CVD surface modification research has created over the last 20 years. In this regard, the lack of related economical production solutions has hindered commercialization efforts. 
     US patent application 2014/0113074 A1 is directed to a graphene manufacturing process utilizing a Cu foil substrate roll, which together with a gas porous material layer, is rolled up into an Archimedes spiral roll. However, the gas porous material interferes with local surface processing, and hinders the growth of undisturbed, higher quality nano-structured materials like carbon nanotubes and silicon nanowires. 
     Nearly all prior art has remained focused on roll-to-roll CVD systems for providing solutions for increased productivity and lower large area production costs of CVD processed flexible substrates. Such an approach, however, necessarily requires that the length and/or size of the CVD reactor chamber be increased. Additionally, the processing conditions developed with batch process CVD systems used for research and development (R&amp;D) are typically not directly portable to roll-to-roll CVD systems, which then typically requires multiple generations of pilot system development prior to scale up to a production roll-to-roll CVD system. This thus increases the capital cost, development risk and commercialization time frame of roll-to-roll CVD projects, often putting it out of reach for many smaller/startup corporations. As a result, the scale up of large area CVD processed films and/or nano-structured material covered flat substrates has, in the past, only been implemented commercially on a selective basis for high volume applications. It will be appreciated that this type of a project risk typically could be afforded only by large corporations with preexisting product sales channels. 
     There is therefore a need in the art for the ability to transfer processes for nano-structured materials or thin film surface modifications utilizing flexible substrates and developed on batch process CVD systems to volume production with batch process CVD system solutions that are less risky and costly to scale up. In addition, it is desirable that such batch process solutions allow processing of one or more rolls of flexible substrates. Further, it is desirable that such a system solution be adaptable to a range of CVD processing needs, without costly hardware changes or upgrades. 
     SUMMARY OF THE INVENTION 
     It is a first objective of this invention to create a manufacturing solution compatible with a batch R&amp;D CVD system that enables the CVD processing of a roll of a flexible material in a substantially uniform manner. 
     It is a second objective of this invention to enable the CVD processing of at least one flexible substrate with a CVD batch process system where the length of the flexible substrate is greater than 5 times the diameter or width of the respective CVD reactor chamber. 
     It is a third objective of this invention to be able to utilize substantially similar process recipes for both R&amp;D CVD batch reactors processing a flat substrate and CVD batch reactors of this invention processing a 5-100× larger flexible substrate area. 
     It is a fourth objective of this invention to have similar CVD system designs and hardware for CVD processing of flexible substrates for a range of CVD processes. 
     It is a fifth objective of this invention to enable the growth of a nano-structured material over at last one surface of a rolled up flexible substrate that is located inside a process chamber of a CVD System. 
     It is a sixth objective of this invention to provide a system solutions for both hot wall and cold wall CVD processing of large area flexible substrates. 
     It is a seventh objective of this invention to lower the production cost and development cost for scaling up CVD processing of flexible materials 
     It is an eight objective of this invention to provide a method to remount a flexible substrate roll to that is can be processed as a whole in a batch CVD process. 
     These and other objects of the present invention are accomplished by the novel substrate remounting method of this invention and its utilization in the batch process CVD synthesis. This substrate remounting method requires the unrolling of a flexible substrate roll, and the subsequent re-rolling of such substrate roll into an Archimedes spiral in such a manner that each layer (of the roll) is spaced apart by two or more gas porous strips that provide both a constant spacing function and the process gas exchange between the inner and other regions of such remounted substrate roll. 
     The CVD processing of flexible substrates is intended to include any type of CVD processing of flexible process compatible substrates having a thickness that is less than 1/25 of the longest dimension of the substrate. Examples of such flexible substrates are stainless steel, copper, platinum and plastic foils in the 10-200 μm thickness range. Of course, the process temperature stability of a given substrate generally determines the suitability of a given substrate for a given CVD process. For example, ultra-low temperature CVD processes are suitable for plastic films, which are typically processed at a temperature of less than 100° C. 
     The term CVD Synthesis in the context of this invention is intended to include any precursor gas, or liquid film deposition, or wetting, or any solid or powder coatings laid on top of the substrate that can then be converted into a usable surface modification, or nano-structured material growth with gas and/or liquid delivery system and with a heating solution (either external or internal) that is able to sufficiently isolate a respective process region from the outside atmosphere and to deliver a required time dependent heat profile. It is intended to also include continuous, pulsed and time sequenced (atomic layer deposition with self-limiting process gas exposures) precursor dispensation onto the substrate area and it includes all pressure ranges suitable for a given CVD process, i.e., ranging from 10 −6  mTorr to 760 Torr and higher. 
     Typically, C 2 H 4  is used as a preferred carbon-containing precursor gas for carbon nanotube growth. However, gases such as C x H y  (e.g., C 2 H 2 , C 2 H 4 , CH 4 , etc.), ethanol, and methanol can also be used. Ar or N 2  are typically used as inert process gases (push gas). H 2  and optionally an oxygen-containing gas, e.g., O 2 , H 2 O or Ozone, are typically utilized in one or more process steps. SiH 4 , or HSiCl 3  or SiCl 4  is often used for silicon nanowire growth and nickel carbonyl, for example, can be used to deposit a Ni film onto a surface. 
     The heating of the flexible substrate can happen via an external heating source (resistive oven, infrared, radio frequency induced) or via an internal direct or alternative current flowing through a partially conductive flexible substrate, and the CVD process can be a hot wall or cold wall process. 
     It is contemplated that the substrate remounting method of the present invention can be retrofitted into existing CVD systems for increased production capacity, and that customized CVD system designs with optimized loading capacity in accordance with this invention, together with custom tuned CVD processes, can provide cost optimized production solutions for each given nano-structured material or surface modified flexible substrate manufacturing challenge. 
     Thus, this invention relates, at least in part, to CVD batch processing systems enclosing one or more flexible substrates with one or two-sided catalytic active surfaces that in total have a large usable surface area on which such nano-structured materials can be synthesized. Another aspect of this invention addresses economical CVD process solutions for surface modification of flexible substrates, such as increasing the corrosion resistance of steel foil by enriching its surface layer with suitable chemicals, e.g., Ni, Cr, C, to make such layer more “stainless steel-like”. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art R&amp;D CVD process chamber. 
         FIG. 2  shows a process gas accessible remounted substrate roll. 
         FIG. 3  shows a CVD reactor with a horizontal process tube and a horizontally oriented remounted substrate roll. 
         FIG. 4  shows the theoretical length capacity of a remounted substrate roll versus the inner diameter of a respective process tube for different substrate layer gap values. 
         FIG. 5  shows multiple remounted substrate rolls loaded into an asymmetric process tube. 
         FIG. 6  shows multiple remounted substrate rolls loaded in a symmetric process tube. 
         FIG. 7  shows a CVD reactor with a vertical process tube and a vertically oriented remounted substrate roll. 
         FIG. 8  shows a method to create a remounted substrate roll 
         FIG. 9  shows a method for the CVD processing of a remounted substrate roll 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the components of a prior art R&amp;D CVD horizontal tube furnace system, which includes a heated process chamber  10 . The chamber  10  includes a gas ring  12 , an end cap  14  and a asymmetric process tube  16  with a narrowed down neck exhaust gas port  18  on one side and a flange  22  on the other side. The chamber  10  is formed by a sealed arrangement (i.e., with o-rings and cooling to protect the seals) of gas ring  12 , process tube  16 , end cap  14 , and all respective entry and exhaust gas ports. The process tube  16  is surrounded (at least during part of the CVD processing time) by a resistive oven  30 , which can have multiple individually controllable heating zones  32 , insulating end zones  34 , and optionally flexible and removable insulating structure  36 , i.e., flexible insulating collars made from quartz fibers or ceramic wool, between the oven end zones  34  and the process tube  16 . Various systems/methods (not shown) are used in prior art systems for injecting and distributing one or more process gases into the chamber  10 . Inside the chamber  10  a substrate holder  24  is used to locate and support a substrate  26  for CVD processing. Alternatively, in prior art CVD systems, a thin flexible substrate  26  having a width that is typically less than ½-¾ of the full inner circumference of the process tube  16  is placed on the bottom of the tube  16  without any holder  24 . Alternatively, in prior art systems, a flexible substrate is rolled and crimped into the shape of a hollow cylinder shape, and optionally is supported on the inside by a hollow quartz liner. For prior art CVD systems, such thin and flexible substrates  26  can therefore, at a maximum, be as long as the circumference of the process tube and as wide as the uniform heated zone of the process tube, i.e., the usable area between the length of the heating zone and 1-3×Ø, with Ø=inner diameter of the process tube  16 . 
       FIG. 1  shows a particular embodiment of the prior art where the substrate holder  24  is secured to a transfer arm  38  that is held and connected to the end cap  14  through a seal  42 , and is additionally mechanically supported with a bracket  44 . The arm  38  is also shown to be hollow on the inside and to hold multiple thermocouples  46  terminated at different distance from the end cap that can be used to control matching multiple heating zones  32 , respectively. Additionally, one or more thermal baffles  48  (e.g., light scattering white quartz discs) are shown located on the arm  38  that reduce the heat loss from the heated section of the process tube towards the gas ring  12  and end cap  14 . 
     Other prior art research CVD systems use a symmetric straight process tube that extends a significant distance beyond the oven  30 , with each end connected to respective end caps in a sealed and sufficiently air or water cooled manner. 
     The width and length or diameter of a single substrate  26  that can be inserted into a given process tube  16  and successfully processed with a respective prior art CVD systems is thus limited by the inside diameter Ø of the tube  16 . To increase the productivity of such prior art CVD systems for the case of rigid round wafer substrates, such substrates may be positioned vertically in a wafer boat with equal spacing between them and oriented parallel to the end cap, i.e., perpendicular to the main gas flow direction inside the tube  16 , to allow process gas to get in between them. Thus, while this provides the option of processing more surface area, it still prevents the option of processing a flexible substrate having a length that is significantly longer than 3 times the inner diameter Ø of the tube  16 . 
       FIG. 2  shows several embodiments of this invention in the form of a process gas accessible mounted substrate roll  100  that includes a remounted substrate roll  110  with individual layers  112  and an inner (or optionally outer, not shown in  FIG. 2 ) support tube  114  that is longer than the width of the substrate stack  120 . At least two, approximately equally thick, flexible and gas permeable spacer strips  116  are laid above the top active surface  118  of a long stack  120  so that each strip  116  at least partially overlaps one of the two long side edges  122  of the surface  118 . Alternatively, the strips  116  can be placed below the stack  120 . 
     The combination of the stack  120  and spacer strips  116  is then rolled into a tightly wound roll, thus forming the remounted substrate roll  110 , with its multiple layers  112  separated by the thickness of the strips  116 . If the thickness of the strips  116  is constant along its length, then roll  110  may also be referred to as an Archimedes spiral roll. The thickness of the two strips  116  can optionally change along their length to allow an intentional controlled variation of the gap between the layers  112  as they progress from the most inner to the most outer layer of the roll  110 . In a different embodiment of this invention, one or more additional gas permeable strips  116  can be placed between the two outer strips  116  to prevent the local collapse during CVD synthesis of a stack  120  that is wider than the stiffness of the stack  120  allows without it. The strips  116  allow for the process gases to enter the gap between the layers  112  from both sides and to diffuse along the length and width of the stack  120  thus helping with creating a more uniform gas environment inside the roll  110 . 
     In further embodiments of this invention, the stack  120  may include a single substrate sheet  126  with only one active surface  118 , a single substrate  126  having two opposing active surfaces  118 , two substrates  126  each having a single side active surface  118 , or one substrate  126  laid on top of the other so that both active surfaces  118  are located on the outside of the stack  120 . 
     In another embodiment, the stack  120  is formed by a single substrate  126  with a top side active surface  118  that is supported by a stiffener  128  in the form of a single or multiple thin sheets made from an inert material that is compatible with the chosen CVD process. Such a stiffener may be thicker than the substrate sheet  126 , and optionally be somewhat compressible in the radial direction of the roll  110  to minimize the wrinkling of the roll  110  during CVD processing due to differential thermal expansion differences of the material comprising the roll  100 . Such a vertical compressibility with simultaneous stiffening properties in the width direction of the material  118  can, for example, be achieved by a slight sinusoidal corrugation of a metal foil with the corrugation waves being aligned parallel to the axis of the roll  110 . 
     In a further embodiment, two single substrates  126  sandwich a stiffener  128  and have opposing external active surfaces  118 .  FIG. 2  shows such an embodiment where the stiffener  128  is sandwiched between two substrates  126  to allow the building of wider rolls  110  than the substrate or substrate pairs  126  allow on their own (without risking local gap changes during CVD processing) and without any additional strips  116  added between the two primary side strips  116  located near the long edges  122  of the stack  120 . In one embodiment of this invention, the stiffener  128  has a similar thermal expansion coefficient as the substrate  126 , or even more preferably, is made from the same material to minimize thermal expansion variations. In another embodiment of this invention, the stiffener is made from carbon and may include, for example, GraphFoil® (manufactured by GrafTech International Holdings), carbon paper (manufactured by Torray), and carbon felt. It can also be straight or on dimensional corrugated metal foils that are not active for a chosen CVD process, for example Cu and many other metal foils that by themselves are significantly catalytically inactive during the CVD based CNT growth. 
     The spacer strips  116  are gas permeable to allow easy gas access to the gap between two adjacent layers  112  along the long edges  122 , and preferably are made from process compatible materials. Example of such strips  116 , depending on the chosen CVD process, include nano-carbon paper, flat, perforated and/or grooved GraFoil®, non-woven carbon fiber paper, woven carbon fiber cloth, threads of carbon fibers, and ceramic cloth. Alternatively, a material that has a similar material composition to the substrate  126 , for example in the form of a sintered, woven or foam like material, can be used to manufacture process compatible strips  116 . Preferably, strips  116  allow for minor movement of the stack  120  positioned thereunder or above due to the thermal expansion of the stack  120 , thereby reducing the tendency of kinking in the stack  120  during the heating and cooling process steps of the CVD Synthesis. The material for spacer strips  116  is preferably chosen to prevent layers  112  from locally welding to such strips and thereby to each other. Strips  116  can be made from a single material or be a composite of multiple materials, e.g., a 0.5 mm thick flat, sintered or corrugated (for enhanced gas permeability) stainless steel, Ni or Cu porous strips or foam sandwiched between two flat (e.g., 25-100 μm thick) and substantially gas tight (for minimal Cu vapor penetration) nano carbon papers strips (manufactured for example by CVD Equipment Corporation from 5-25% by weight of mm long carbon nano tubes and the rest from exfoliated graphite, or using strips cut from high density PGS sheets manufactured by Panasonic) or Grafoil® to better match the thermal expansion of the substrate  126  and to prevent any welding of the substrate  126  to such composite strips  116 . 
       FIG. 2  shows one of many possible mounting options of a roll  110 , i.e., internally supporting the roll with an extended hollow tube  114 . The material of the tube  114  preferably has a similar expansion coefficient or is made from the same material as the flexible substrate  126 , to minimize differential expansion between the roll  110  and the tube  114 . The above-disclosed mounting schemes (internal or external mounting tube) of the remounted substrate roll  110  are not intended to be limiting. Other mounting schemes will be obvious to those skilled in the art, and are intended to be included in this invention. 
     As long as a process compatible combination of the various materials chosen to manufacture the support tube  114 , the spacer strips  116 , the flexible substrate foils  126  and optional stiffening sheets  118  have negligent influence on the outcome of the chosen CVD Synthesis, and sufficiently thick and porous strips  116  are selected, then large area, lower cost manufacturing of flexible substrate coated with thin films or with nano-structured materials may be achieved in substantially similar style tube furnace CVD reactors. In other words, this invention allows for the CVD processing of rolls of flexible substrates that can be much longer than the diameter of a given process tube without the need to switch to a roll-to-roll system or to substantially change the CVD processing conditions. 
     Optionally, depending on the springiness of the stack  120 , it may be desirable to secure one or both ends of the roll  110  to prevent unwinding of such roll during transport and/or subsequent CVD processing. The securing of the ends of the roll  110  may be accomplished with carbon or SiC fiber threads, metal wire, metal wire mesh, metal foam, expanded metal sheets, non-woven or woven carbon fiber or metal wire fabric, flexible fabric, felt or mesh that has been sewn together into a continues sleeve, multi part assemblies designed to allow to reversibly change their inner or outer diameter, (i.e. Chinese finger cuffs), gravity assisted mechanism (i.e. pulley) that help to keep the roll  110  tight during handling and CVD processing. Again, a preferable option is to utilize wires or bands made from the same material as the substrate  126  to minimize thermal expansion differences. For example, a sleeve can be made (crimped) from the same material as the substrate  126  that keeps the roll  110  together mechanically during transport and CVD processing. 
     In one embodiment of this invention, the flexible substrate  126  is a metal foil. For example, to grow vertically aligned carbon nanotubes (VACNT) an alloy including Fe, Ni, Cr, (e.g., a 304 or 316 stainless steel foil) can be used as a base substrate, and then over coated at least on one side with a catalytic active material film. For example, to make one or both sides of such a foil catalytically active for VACNT growth, a preferably thin 5-50 nm Al 2 O x  barrier/diffusion limiting intermediary thin film is first deposited onto the metal foil and then covered with a 0.5-5 nm thick Fe, Ni, Co, MoC, FeNi, etc. catalytic active film. Such films can be deposited by e-beam, sputtering, liquid film deposition, etc. Optionally, a bonding layer, for example a 5-50 nm Fe-film, can be deposited before the Al 2 O x  layer to improve the adhesion. A wide range of catalytic active transition metal thin films have been shown to be able to grow VACNT&#39;s, either with none or with matching barrier intermediary thin film layers, and all of them are suitable candidates for this invention. 
     Alternatively, to grow silicon nanowires (SiNW), a 1-20 nm thin film Au layer can be deposited on a range of metal foils (e.g., SS 316 or SS 304) and/or open cellular foams sheets or onto flexible foils covered with another thin metal film (e.g., Ni, Cu, etc.). Such coated substrates can then be used for SiNW (Au thin film on SS foil) or SiNi NW (Au+Ni thin film on SS foil) or SiCu NW (Au+Cu thin film on SS foil or Au thin film on Cu foil) growth via CVD processing in the 450-700° C. range utilizing SiH 4  and H 2  as the primary active precursors gases. The intermediary layers (e.g., Ni, Cu) can alloy with the Si to form alloyed NW&#39;s or NW with core-shell structure, where one material is preferably located on the inside of the NW and the other is either located in the outside or both inside and outside the NWs. 
     Such single or double layer catalytically-active films can be created, for example, by physical vapor deposition (e.g., ebeam, sputtering, thermal evaporation, etc.) or liquid film deposition of dissolved catalytically-active material (for example ferrocene dissolved alcohol) and subsequent solvent evaporation. 
       FIG. 3  shows an embodiment of this invention where a mounted roll  110  is loaded axially inside a horizontal tube furnace CVD system, thus forming a high capacity CVD System  200  of the present invention where the process gases flow along the axis of the mounted roll  100 . In the specific embodiment shown in  FIG. 3 , the support tube  114  is located with respect to a transfer arm  202  having a location stop  204 , and is mechanically supported by standoff pins  206  that provide minimal thermal contact between the tube  114  and the arm  202 . Other structure for supporting the support tube  114  is also contemplated herein, e.g., utilizing the shaft of the transfer arm  202 , or utilizing blocks sitting inside the process tube to support and locate the internal tube  114  or equivalent external support tube. 
     Thus, the present invention allows a prior art tube furnace CVD system, typically used for substrate sizes that are smaller than the diameter of the respective process tube  16  or for flexible substrate  26  that are equal or narrow than the diameter of the process tube  16  or at least not longer than the circumference of the tube  16 , to be utilized for scaled-up production of nano-structured materials. More particularly, it has been discovered herein that the replacement of prior art transfer arm  38  with the transfer arm  202  disclosed hereinabove, together with the disclosed remounted substrate roll  110 , provides a scaled-up system which in turn allows the CVD processing of a flexible substrate  126  that can typically be 10-100 times longer than the inner diameter Ø of the tube  16 , depending on the chosen thickness of the strips  116  (typically 0.05 mm-10 mm) which need to selected with respect to the width of the roll  110  and the chosen CVD process conditions. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Substrate area gain possible with the present invention over prior art utilizing a 
               
               
                 single flat substrate having a length = 79% of inner diameter Ø of the process tube. 
               
             
          
           
               
                   
                   
                   
                   
                   
                   
                 area gain 
                   
                 area gain 
                   
                 area gain 
                   
                 area gain 
               
               
                 Process 
                 Process 
                 typical 
                 D0 = 
                 D1 = 
                 Length 
                 for 2-sided 
                 Length 
                 for 2-sided 
                 Length 
                 for 2-sided 
                 Length 
                 for 2-sided 
               
               
                 tube ID 
                 tube ID 
                 flat foil 
                 inner 
                 outer 
                 of foil 
                 foil 
                 of foil 
                 foil 
                 of foil 
                 foil 
                 of foil 
                 foil 
               
               
                 diam- 
                 diam- 
                 substrate 
                 diam- 
                 diam- 
                 substrate 
                 substrate 
                 substrate 
                 substrate 
                 substrate 
                 substrate 
                 substrate 
                 substrate 
               
             
          
           
               
                 eter 
                 eter 
                 width 
                 eter 
                 eter 
                 0.5 mm gap 
                 1 mm gap 
                 5 mm gap 
                 10 mm gap 
               
             
          
           
               
                 [inch] 
                 [mm] 
                 [m] 
                 [mm] 
                 [mm] 
                 [m] 
                   
                 [m] 
                   
                 [m] 
                   
                 [m] 
               
               
                   
               
             
          
           
               
                 5 
                 127 
                 0.1 
                 25 
                 102 
                 15 
                 151 
                 7.7 
                 76 
                 1.5 
                 15 
                 0.8 
                 7.6 
               
               
                 6 
                 152 
                 0.12 
                 25 
                 122 
                 22 
                 184 
                 11 
                 92 
                 2.2 
                 18 
                 1.1 
                 9.2 
               
               
                 8 
                 203 
                 0.16 
                 25 
                 163 
                 41 
                 251 
                 20 
                 125 
                 4.1 
                 25 
                 2.0 
                 13 
               
               
                 10 
                 254 
                 0.2 
                 25 
                 203 
                 64 
                 314 
                 32 
                 157 
                 6.4 
                 31 
                 3.2 
                 16 
               
               
                 13 
                 330 
                 0.26 
                 25 
                 264 
                 108 
                 411 
                 54 
                 205 
                 11 
                 41 
                 5.4 
                 21 
               
               
                 18 
                 457 
                 0.37 
                 25 
                 366 
                 209 
                 573 
                 105 
                 286 
                 21 
                 57 
                 10 
                 29 
               
               
                 22 
                 560 
                 0.45 
                 25 
                 448 
                 314 
                 702 
                 157 
                 351 
                 31 
                 70 
                 16 
                 35 
               
               
                 40 
                 1016 
                 0.81 
                 25 
                 813 
                 1037 
                 1,276 
                 519 
                 638 
                 104 
                 128 
                 52 
                 64 
               
               
                   
               
             
          
         
       
     
     Table I shows the theoretically maximum obtainable length and processable area gain of a flexible substrate transformed into a roll  110  having a 25 mm inner diameter and an outer diameter that is 79% of the inner diameter Ø of a given process tube  16 . The length of the flexible foil and therefore also of the surface area gain is approximately inversely proportional to the height of the spacer strip  116  for multiple turn Archimedes spiral rolls (constant thickness strips  116 ) when the thickness of the stack  120  is much smaller than the height of the strips  116 . The data from Table I is also displayed in  FIG. 4 . The larger the diameter Ø, the higher the capacity gains for this invention for a fixed inner diameter of the support tube  114 . The area gain of this invention in maximum usable surface area over prior art is approximately linearly dependent on the diameter Ø. For example, to grow a 2 mm tall vertically aligned carbon nanotube array on stainless steel foils, at least a 6 mm gap between the layers  112  is needed. Depending on the width of the substrate  126 , an even larger gap may be needed for uniform height growth along the axis. 
       FIG. 5  shows further embodiments of this invention where multiple remounted substrate rolls  110  are loaded axially inside a horizontal CVD processing chamber  300 , thus enabling the building of a high capacity CVD processing system in accordance with the present invention. The furnace for the processing chamber  300  is removed for clarity in  FIG. 5 . The CVD processing chamber  300  includes a transfer arm  302  with a stop  304 , and optional multiple standoff pins  306  to minimize thermal heat sinking of a support tube  308 . Only an internal support tube is shown in  FIG. 5 , but it should be understood that an external support tube can be used equivalently. Each roll  110  has two narrow side strips  116  to control the spacing of each layer  112 . Process gas is delivered between two adjacent roll  110  pairs from the outside gap between the rolls  110  and the inner wall of the process tube  16  thus feeding the rolled substrates inside each roll  110  from both long edges  122 . 
       FIG. 5  also shows the additional optional embodiment of this invention wherein support tube  308 , onto which multiple rolls  110  are mounted, is closed at one end with a cap  312  and has holes  314  between two adjacent rolls  110  to facilitate the delivery of process gas to the gap between two adjacent rolls  110 . An auxiliary removable gas injector  322  is mounted to a gas port  324  located on the inside of the end cap  14  in a sealed manner, and is supported by a fork  326  that is attached to the transfer arm  302 . The respective thermal baffles  48  have cutouts to allow injector  322  to extend therethrough. The exit end  328  of the injector  322  is located near an entry port  332  of a distributor  334  that is connected to the open end of the support tube  308  in such a manner that most of the process gas exiting the end  328  is directed into entry port  332  of distributor  334 , and from there to the interior of the support tube  308  from where it escapes through the holes  314  into the gaps between two adjacent rolls  110 , thereby providing gas flow into this gap to increase the process uniformity for each individual roll  110 . Optionally, the entry  332  of the distributor  334  is made from a removable seal that forms a quasi gas tight seal with the exit end  328  of the auxiliary injector  322 . Optionally, the exit end  328  of the injector  322  is also capped and has a side hole nearby to eject the process gas perpendicular to the gas injector axis  322 , and into the distributor  334 . Optionally, a pin(s) can be inserted into one of the holes  314  to further help locate one of the ends of a roll  110  with respect to the support tube  308 . In this arrangement, the remaining open holes  314  are capable of delivering a sufficient quantity of process gas into the gaps between the adjacent rolls. 
     The gap between the rolls  110  is preferentially chosen, depending on the available process conditions and gas flow delivery, to allow sufficiently uniform CVD Synthesis for each roll  110 . 
       FIG. 6  shows additional multiple embodiments of this invention in the form of a CVD process reactor  400 . A symmetric straight process tube  402  is shown with two different end termination versions. The right end of the process tube  402  has a straight tube end that is sealed with an o-ring seal  404  positioned between the right end cap  406  and a screw-on compression ring  408  that compresses the o-ring  404  and thus seals the end cap  406  to the process tube  402 . This style end-cap seal is typical for many lower cost R&amp;D CVD systems, and is typically found on both ends of the respective process tube. The left side of the process tube  402  also has a straight end, but additionally includes a flange  412  welded thereto. Flange  412  is sealed to gas ring  416  via at least one o-ring  414 , the o-ring  414  being compressed by a clamp  418  pressing against an edge of the flange  412 . The other side of the gas ring  416  has at least one o-ring  422  that seals to a removable end cap  424 . The gas ring  416  has at least one gas port  426  with at least one internal gas channel for delivering at least one process gas to the inside of the process tube  402 , and optionally (not shown in  FIG. 6 ) to internal gas delivery channels inside the end cap  424 , which then delivers process gases to at least one gas port that connect to one or more optional internal gas injectors (also not shown in  FIG. 6 ) or other internal gas ports. An optional transfer arm  432  is sealed and connected to the end cap  424  with a seal  434 , and is additionally supported with an optional holder  436 .  FIG. 6  also shows the example of two removable thermal baffles  438  and  442  in the form of an evacuated and sealed quartz cylinder filled with ceramic wool  444 . Each baffle is located near a respective end cap, and an internal mounting tube  446  and  448 . A fixed locating pin  452  on the transfer arm locates the baffle  438 , and the removable pin  454  both locates the baffle  442  and allows for its quick removal from the transfer arm  432  to allow loading of one or more substrate rolls  110  mounted on a support tube  456 . Locating pin  458 , together with the thermal isolating standoff pins  462 , provide a reproducible location function for the support tube  456 .  FIG. 6  shows the example of a furnace  470  which surrounds the processing zone of the process tube  402  having outer insulation zones  472  and inner individually controllable heating zones  474 . Additional optional insulating zones  476 , together with the thermal baffles  438  and  442 , can be used to further reduce the radiation loss from the heated part of the process tube and provide a more uniform temperature zone for the processing zone of the CVD synthesis system holding at least one roll  110 . The inside of the hollow sealed transfer arm  432  can hold one or more thermocouples  46  that can be used for feedback control of the heating zones  474 . 
     Process gas is preferably directed into at least one gas port  426 , flows through the gas ring  416  and/or the end cap  424 , and then exists through a hole  478  in the end cap  406 , and through an exit port  482 . Alternatively, the process gas can escape through a respective gas port in the gas ring  416 . 
       FIG. 7  shows additional embodiments of this invention in the form of a vertical CVD process chamber  700  that holds at least one vertically oriented roll  110  with an inner support tube  702  that has an optional attached porous support plate  703  at its bottom end. The bottom of the bottom roll  110  is supported by the gas permeable plate  703 . The tube  702  extends beyond the top spacer strip  706 , and has an optional handle  707  that allow for the grasping, lifting and transport of the support tube  702  with at least one loaded substrate roll  110  and for the placing/removal of support tube  702  on/from a support table  708 . This grasping and lifting can be done manually or robotically. If multiple vertical rolls  110  are being used, they can be supported by auxiliary porous support means, i.e. removable bars, removable porous disk located by removable pins placed through the support tube  702 . The table  708  is shown in the form of a hollow body with internal support posts  712 , with a gas permeable top section  714  across the extent of the bottom end of the roll  110 , and with a non-gas permeable top section  716  to channel process gas into the roll  110 . Standoff legs  718  support the table  708  and one or more thermal baffles  722 . The exit end  724  of a gas injector  726  is located either inside or near an entrance hole of the hollow body of the table  708 , thus allowing process gases to reach between the individual layers of the substrate roll  110  by first being spread uniformly through the hollow body of the table  708 , then through the gas permeable section  714  of the support plate  703 , and subsequently through the gas permeable spacer strip  704 . If multiple rolls  110  are supported by the tube  702 , process gas reaches the 2nd and higher roll  110  through the gas exiting the top strip  706  of the lower placed roll  110 , and optionally through process gas going around the lower rolls  110  and/or through optional side holes in the support tube  703  allowing process gas to enter and exit at different height along the tube  702  (not shown in  FIG. 7 ). The exit end  724  of the injector  726  can optionally be sealed with process compatible gaskets to the table  708 , and can have a cap at the end and side holes nearby to allow the process gas to eject sideways into the table  708 . 
     The sealed CVD process chamber is primarily formed by a vertically oriented bell jar type process tube  732  with a welded flange  734 , a support ring  736 , a base plate  738 , and top and bottom o-ring seals  742  and  744 . The flange  734  is pressed by a mounting ring  746  against the seal  742 . The plate  738  is preferably pressed against the seal  744  with a spring loaded translation mechanism to allow easy loading and off-loading of the roll  110  mounted on the support tube  702 . A sealed thermocouple sleeve  748  located inside the tube  702  with a gas tight seal  752  at the base plate  738  can hold one or more thermocouples  46 , with each thermocouple  46  providing a process temperature feedback signal that can be used to control a heating zone  754  of a furnace  760  having additional insulating zones  762  at its bottom and top end. Clearance holes  764 ,  766  and  768  in the thermal baffles  722  and table  708  allow interference free passage for the removable injector  726  and the removable shield  748 . An o-ring seal  772  is preferably located at the end of injector  726 . One or more pressure sensors  774  may be connected to the base plate  738  or ring  736  through a respective sealed gas line  776  to allow the monitoring of pressure inside the process tube  732 . The removal of process gas from the process chamber is done through an exhaust port  778  and an optional internal gas shield  782  that forces the process gases to primarily go from the inject line  726  through the support roll(s)  110 , and then uniformly escape between the inner walls of the process tube  702  and the other wall of the shield  782  towards the exhaust  778 . Optionally, the process gas can also be exhausted through the gas port in the top of the process tube  732  and furnace  760 , or through other appropriately placed exhaust ports. 
     The minimum acceptable height of the strips  116  (and therefore the maximum achievable area gain with this invention over conventional prior art flat single substrate R&amp;D systems) depends on the length of the flexible substrate, the process condition of the CVD Synthesis, the flow rates and residence time of the process gases in the process tube, and the type of nano-structured material to be grown on the catalytically-active substrates, and typically needs to be optimized for each new CVD Synthesis processing opportunity to maximize productivity and minimize the production cost. For example, in order to grow a 2 mm size VACNT, one must assume that a minimum gap of 6 mm or more is needed for double sided VACNT growth on 20-150 μm thick SS flexible foil substrates with double sided coated catalytic active surfaces  118 . If, on the other hand, SiNW or Si-allow NWs are grown on narrow foils &lt;75 mm, smaller heights of spacer strips  116  are potentially possible for lower pressure CVD operations. Similarly, if the purpose of a given CVD synthesis is mass production of a surface film modified steel sheet with less than 10 μm thick Si, Cr, Ni films or stainless steel-like alloy films, to provide, for example, increased corrosion resistance, i.e. more stainless steel-like surface, tighter gaps are acceptable to increase production size per batch and lower the production cost per coated surface area. 
     This invention thus allows the CVD process and system hardware developed during an R&amp;D phase of the nano material growth or CVD thin film process development to be ported over to a scaled up production system. Further, a relatively minor upgrade to an existing prior art CVD System allows, in many instances, a significant improvement (5×-100×, depending on the gap between the layers  112 ) in the production capacity of a given tube furnace system. 
       FIG. 8  shows a further embodiment of this invention and, more particularly, the process steps for transforming a flexible substrate roll into a remounted substrate roll, and then processing it via a CVD process to create a large area CVD processed surface area without the utilization of a roll-to-roll system. In step  2002 , a substrate foil is simultaneously unwound while any respective separator layer is simultaneously removed, and then rewound with the addition of at least two spacer strips  116  to form a spiral wound roll with each substrate layer spaced apart by a spacer strip near the long edges of the flexible substrate roll, thus forming a roll  110 . In step  2004 , at least one remounted substrate roll is inserted into a horizontal or vertical tube furnace and subjected to a CVD process, thus processing the whole substrate roll in a batch mode process. 
       FIG. 9  describes another embodiment of this invention and, more particularly, the process steps for the CVD processing of a continuous flexible substrate roll in a CVD batch processing system. After creating at least one remounted substrate roll  110  in step  2010 , and inserting it into a horizontal or vertical CVD tube furnace system in step  2012 , the heating uniformity of the remounted substrate roll is enhanced by a close to atmospheric process operation in step  2014  in an inert atmosphere that pushes hot process gases through the gaps between the individual layers of the roll. Such heating can be enhanced, for example, by adding a fan to a quasi-sealed CVD process chamber (minimum gas exit to conserve heat losses) made from process compatible material (e.g., a quartz fan) to help with heating the metal foil by increasing the gas recirculation and convection heating the inner part of the roll  110  with hot gases. Subsequent CVD processing in step  2016 , and offloading in step  2018 , yields a CVD processed roll of flexible substrate. 
     Of course, the remounting of the substrate roll can be in line with the catalytic film deposition (if needed for the CVD process) onto the substrate roll to minimize the handling of the substrate roll. 
     While only selective embodiments of this invention have been discussed above, it should be understood that combinations of the above mentioned embodiments, as well as obvious modifications thereof, as easily understood by the skilled in the arts, are therefore intended to be included in this disclosure.