bluuebunny/crossref_metadata_2025 huggingface dataset:
Grazing-Incidence X-Ray Diffraction Studies of the Relaxation Behavior in Galnas/GaAs Multilayers Grown on GaAs[001]
Authors: Rose Dirk , Pietsch Ullrich
Published: April 2011

The depth profile of the defect structure in strained and partially relaxed Ga0.8In0.2As/GaAs[001] multilayers is investigated with the method of X-ray grazing-incidence diffraction. Both in-plane and out-of-plane parameters are obtained from the subsurface region between five and a few hundred nm.

The strength of the method is demonstrated on a sample series with similar thickness of the Ga0.8In0.2As sublayers, ta, but with varying thickness of the GaAs barrier, tb.The degree of relaxation R is directly obtained from the angular position of the in-plane Bragg peaks. For decreasing ta the peak maximum shifts to smaller angles which indicates an increase of R. Additionally the peak width is enlarged. This is explained by the orientational distribution of strain-reduced microdomains which are formed during the relaxation process. Their average size is estimated from the shape of the truncation rods which are recorded at the angular position of the in-plane Braggpeaks. The resulting size of about 100nm is additionally verified by high-resolution X-ray diffraction. The existence of microdomains is caused by a cross-hatched network of 60° misfit dislocations which is confirmed by TEM-measurements.
Determination of the Bonding Configurations of Carbon Acceptors in InxGa1−xAs and AlxGa1−xAs
Authors: Pritchard R. E. , Newman R.C. , Wagner J. , Maier M. , Mazuelas A. , Ploog K.H. , Lane P.A. , Martin T.
Published: April 2011

The local environments of CAs acceptors in InxGa1−xAs and AlxGa1−xAs have been determined from the localized vibrational modes (LVMs) of both isolated CAs impurities and H-CAs pairs using infrared (IR) absorption and Raman scattering techniques. In as-grown layers of InxGa1−xAs (x<0.1), a single LVM due to isolated CAs acceptors was observed. The introduction of hydrogen led to the formation of H-CAs pairs and a single A1−-mode (stretch) and a single A1+-mode (XH) were observed for the InxGa1−xAs layers. All the LVMs were identified with carbon in CAsGa4 cluster configurations implying that less than 5 % of the detectable carbon atoms were present in clusters incorporating one or more CAs-In bonds. For AlxGa1−xAs, five stretch modes and five X-modes of the H-CAs pairs were observed for 0<x<1 and each mode was assigned to configurations for which the originally unpaired CAs had 0,1,2,3 or 4 Al nearest neighbors. These results show that carbon does not appear to form bonds with In atoms for the InxGa1−xAs samples investigated and this can explain the difficulty found in incorporating CAs acceptors in InxGa1−xAs with x>0.1 for some growth techniques. CAs acceptors can form strong bonds with both Al and Ga atoms, however, leading to a high solubility of carbon in AlxGa1-xAs over the full compositional range.
Low Temperature Grown Thin Inalas Step Graded Buffers for Application on Optical Modulator at 1.3 μM
Authors: Shen Lei , Wieder H. H. , Chang W. S. C.
Published: April 2011

Preliminary results are described about the growth, structure and properties of multiple quantum well(MQW) Quantum Confined Stark Effect (QCSE) modulators grown on GaAs substrates for operation at 1.3μm in wavelength. Step graded InAlAs buffer layers grown at low temperature by molecular beam epitaxy (MBE) with a total thickness of 0.3 μm are used to relieve the strain caused by the lattice-mismatch between the GaAs substrate and the In0.35Ga0.65As/In0.35Al0.65As MQW heterostructure. X-ray diffraction spectra show that significant lattice relaxation takes place in the buffer. A quantum confined Stark shift of the exciton absorption peak of 48meV was obtained with an applied electric field of 130KV/cm, measured in PIN diode structures consisting of 30 period 95ÅIn0.35Ga0.65As/100ÅIn0.35Al0.65As MQWs on a 3 stage compositionally step graded InxAl1−xAs buffer doped with Si to 5*1017/cm3 grown on a nominally 1018/cm3 n-type doped GaAs substrate.
Study of Highly Strained Single InAs−In0.53Ga0.47As Quantum Wells from Phonon Modes by Raman Scattering
Authors: Quagliano L. G. , Orani D. , Ricci A. , Simeone M. G. , Bruni M. R.
Published: April 2011

We report Raman study of highly strained single InAs−In0.53Ga0.47As quantum wells grown by molecular beam epitaxy (MBE) on InP substrates with the well thickness between 4 and 15 monolayers. We have used Raman spectroscopy to characterize quality, disorder and strain of these structures which are of considerable interest for long wavelength optical communications.

In the Raman spectra we have observed an intense narrow line corresponding to the GaAslike LO mode of In0.53Ga0.47As cap layer and a narrow peak due to the LO phonon mode of the InAs layer. These dominant and sharp features characterize the high homogeneity of our samples. In addition to these features we have observed the appearance of distinct peaks with the increase of the InAs layer thickness. In our opinion the presence of these modes is indicative of a slight deterioration of the structural perfection of the sample with the increase of the well thickness. Our investigation shows the ability of Raman spectroscopy to describe these systems and the good quality of our structures.
Measurement and Control of The Indium Composition Profile Near The InGaAs on GaAs Interface During Mbe
Authors: Kaspi Ron , Evans Keith R.
Published: April 2011

The compositional abruptness at both the normal and the inverted InGaAs/Ga(Al)As interface is inherently limited by the surface segregation of In atoms during molecular beam epitaxy. We find, for example, that the intended alloy composition in In0.22Ga0.78As layers is not reached until nearly 35 Å from the normal InGaAs on GaAs interface for growth at 500 °C. We propose and demonstrate a scheme to control and eliminate the compositionally graded region at the normal interface by the artificial formation of an In surface segregated layer (predeposition) prior to the growth of InGaAs.
Mbe Growth and Characterization of (GaAs)l−x(Si2)x and (GaAs)1−x(Si2)x/GaAs Superlattices on GaAs Substrates
Authors: Lee H.P. , Szalkowski F.J. , Zeng X. , Wolfenstine J. , Ager J. W.
Published: April 2011

Lateral compositional graded (GaAs)1-x(Si2)x alloys were deposited on GaAs substrates in a III-V molecular beam epitaxy (MBE) chamber equipped with a electron-beam Si evaporation source. Single crystal GaAs-Si alloys were formed when the deposition temperature was 600°C or higher. The alloys were characterized by Energy Dispersive X-ray Spectroscopy (EDS), Raman scattering measurement and cross-sectional Transmission Electron Microscopy (XTEM). Dislocation-free (GaAs)1-x(Si2)x films of up to x = 0.07 were deposited. For alloys with x between 0.15 < < 0.25, the morphology deteriorates and a high density of stacking faults and micro-twins were observed.
Progress in Modelling Plasma Etch Processes
Authors: Zarowin C. B.
Published: April 2011

This is a progress report on modelling the first of two aspects of plasma assisted chemical processes; it is shown here that by maintaining a constant plasma geometry, observable plasma parameters can be made to determine ion assisted surface chemistry uniquely because the mean energy of ions bombarding the reacting surfaces are thus also uniquely determined. Furthermore, the theory (1) given here sets the stage for another, given elsewhere (2), whicn shows that the resulting processes (i.e., reactive ion or plasma assisted etching and deposition) follow the same “rules”, as thermally driven cnei.lical vapor transport (CVT) for a fixed mean ion energy. Together, these theories permit a considerably more orderly understanding and application of plasma etch/deposition processes than has oeen previously possible.
Microfabricated Tem Sections
Authors: Deckman H. W.
Published: April 2011

A simple convenient technique is described for fabricating 25-5,000Å sized microstructures which are suitable for use as thin sections in transmission electron microscopy. Microstructures are produced by reactive ion beam etching (RIBE) a submonolayer colloidal particle mask, and several effects seen in RIBE are discussed. In particular, it is shown that polymeric deposits formed on vertical side walls can be imaged and etch rates near the surface of some materials can differ substantially from the bulk. The microfabrication technique affords a simple method to study the internal structure of thin deposited films and use of the technique is illustrated with structural studies of amorphous semiconductor superl atti ces.
The Application of Reactive ion Etching to Oxide Films on 150mm Substrates
Authors: Dunfield Stephen , Deacon Tom , Pandhumsoporn Tam
Published: April 2011

The application of reactive ion etching to oxide films on 150mm sub-strates was studied. Etch rates of greater than 450 Å/min for thermal oxide with overall uniformities of less than ±5% have been observed. Selectivity of thermal oxide to polysilicon (20ω per square) has been observed to be in the range of 14:1 to 17:1.
Diagnostics for Process Plasmas
Authors: Dylla H. F. , Manos D. M.
Published: April 2011

This paper reviews the current state-of-the-art of several diagnostic techniques for characterizing, monitoring, and optimizing the properties of process plasmas. The plasma parameters of plasma configurations which are useful for materials processing, such as dc and rf glow discharges, are similar to the parameters of the boundary plasmas in magnetic fusion devices. As a result, much of the large development effort over the last decade on plasma diagnostics for boundary plasmas has direct application in process plasma systems. As particular examples, the authors discuss recent developments of: (1) electrostatic probes for electron density, temperature and power flow measurements; (2) laser fluorescence spectroscopy for ion density and flux measurements; and (3) quantitative plasma mass spectroscopy using quadrupole mass filters.
Spectroscopic Ellipsometry Study of rf-Sputtered a-Ge Films
Authors: Blanco J. R. , Messier R. , Vedam K. , McMarr P. J.
Published: April 2011

Sputtered amorphous germanium films have been examined by spectroscopic ellipsometry. a technique known to yield the void fraction in the bulk of the film,. (and hence a measure of density, ρcalc) with a high degree of precision, Considering the commonly accepted values of the dielectric function and the directly measured density, ρexpt, of Paul, Connell and Tomkin (1973), as the reference data, we reportf that ρcalc for some a-Ge films can be greater than that of crystalline Ge. Examination of the top surface of the sputter deposited films indicates that the highest densities are achieved under conditions of high energy ion bombardment of the film. This study indicates that a more detailed microscopic model of the structure of a-Ge must be considered.
Plasma Deposited Carbosilicon Films from Silane-Phenylsilane Mixtures
Authors: Cutro J. A. , Haller Ivan
Published: April 2011

A series of amorphous silicon/carbon films were deposited from an RF glow discharge in silane-phenylsilane feed gas mixtures with the (ΦSiH3 content varying from 0 to 100 %. The films were characterized with optical and electrical measurements. While the structure of the films deposited from the mixtures contains carbon in more than one configuration the amount of pendant phenyl groups increases as the phenylsilane content of the feed gas is increased. The optical gap, derived from Tauc plots of the absorption spectra, ranges from 1.7 to 2.9 eV, while the refractive index obtained from ellipsometry, ranges from 3.7 to 1.8. The optical gap was found to vary linearly with the carbon atomic fraction in the feed gas, independent of the configuration of carbon atoms in the solid. The refractivity, (n2− 1)/(n2 + 2) , was found to exhibit a similar composition dependence. The room temperature resistivity was observed to increase sharply with increasing carbon content, rising from 107 ohm-cm to 1016 ohm-cm as the ΦSiH3 content of the feed gas was increased from 0 to 25 per cent.
Plasma Deposition of a-Si:H
Authors: Knights John C.
Published: April 2011

There are four easily identified stages in the formation of a hydrogenated amorphous silicon film from an electrical discharge in silane. The first stage is the primary reaction between electrons and silane resulting in a mixture of ions and free radicals. The second stage is the transport of these species to the substrate surface accompanied in parallel by a multiplicity of secondary reactions e.g. ion-molecule, photon-molecule, etc. The third stage is the reaction or adsorption of these species with or onto the substrate surface and the fourth stage is the process by which these species or their reaction products incorporate into the growing film or are reemitted from the surface into the gas phase.
Thermal Nitridation of Silicon in Active Nitrogen
Authors: Giridhar R. V. , Rose K.
Published: April 2011

The dissociation of N2 in a microwave discharge has been studied using a gas phase titration between N(4S) and NO. SF6 added in small concentrations (20–100 ppm of N2) is shown to be an efficient catalyst for dissociating N2. Dissociation fractions [N]/[N2 ] of 4–5% have been obtained. The studies suggest how the partial pressure of atomic nitrogen can be maximized. These results have been applied to thermal nitridation of Si in active nitrogen. A strong dependence of the film thickness on the partial pressure of atomic nitrogen (PN) has been shown. In addition to the nitridation rate, the nitrogen fraction [N]/([N] + [O]) also increases with PN.
The limits of patterning in X-ray lithography
Authors: Cerrina F.
Published: April 2011

We show how the imaging process in proximity X-ray lithography is capable of reaching the sub-100 nm range. However, The use of proximity X-ray lithography is dependent on the mask to form the correct image of the pattern. The joint development of electron beam lithography patterning tools with high-placement accuracy, of a better understanding of the mask mechanical response and of new aligners, clearly indicates that the goal of using X-ray lithography for nanolithography applications is reachable.
Low Thermal Budget Processing Of Organic Dielectrics
Authors: Sharangpani R. , Singh R. , Cherukuri K. C. , Thakur R.P.S.
Published: April 2011

Low dielectric constant organic materials are ideal for use as interconnect dielectrics forintegrated circuits. As compared to silicon dioxide, organic dielectrics with K <3.84 reducepower dissipation, crosstilk and RC delays in interconnects. Curing is essential afterdeposition of these materials to initiate polymerization reactions and form films of desirableelectrical properties. For high performance and reliability, low thermal budget processing isa necessity. Rapid isothermal processing (RIP) based on the use of dual spectral sources isa potential technique to lower the thermal budget. In this paper, we demonstrate the role ofphotoeffects in the curing of polyimide films (K∼2.6) using a rapid isothermal processor witha dual spectral source (Tungsten Halogen and vacuum ultra violet (VUV) lamps) as a sourceof optical and thermal energy. Lamp configurations that allowed a greater availability of ultraviolet and vacuum ultra violet photons on the film to initiate physical and chemical processesallowed a lower curing temperature to achieve the same level of immidization. Furthermore, these samples also gave the lowest leakage current and film stress. Therefore, the rapidheating and cooling features of rapid isothermal processing in conjunction with lowerprocessing temperature through the use of high energy photons to enhance surface reactionsgive superior film properties
Low Dielectric Constant Polymers For On-Chip Interlevel Dielectrics With Copper Metallization
Authors: Gutmann Ronald J. , Chow T. Paul , Duquette David J. , Lu Toh-Ming , Mcdonald John F. , Murarka Shyam P.
Published: April 2011

Low dielectric constant insulators offer the potential of improved interconnection delay and conductor packing density in advanced ICs, both with current metallization schemes and with future technologies such as copper. While polymer materials are very promising in such applications, significant issues must be addressed before oxide-based materials are replaced in mainstream applications. This invited paper reviews the directions of our program, which has emphasized the use of vapor deposited polymers compatible with uniform deposition over large diameter wafers and copper metallization. Therefore, emphasis is placed on polymer material characteristics compatible with inlaid metal (ie. Dual Damascene) patterning.
Investigations Of The Chemical-Mechanical Polishing Of Polymer Films For ILD Applications
Authors: Neirynck Jan. M. , Murarka S. P. , Gutmann R. J.
Published: April 2011

Low dielectric constant films are being investigated as the interlayer dielectric (ILD) in a multilevel interconnection scheme for advanced ULSI circuits. In such applications they will be subjected to planarization processes using chemical-mechanical polishing (CMP), either directly during dielectric planarization or indirectly in the final stages of metal patterning using the Damascene process. In this paper we report the results of our initial investigations of the CMP of three different polymers, all with dielectric constant in the range of 2.3 – 2.7 and with different mechanical and chemical properties. The CMP was carried out using alumina as the abrasive in basic and acidic pH slurries. The effect of preannealing the polymer on the CMP behavior was also investigated
Modification Effects in Argon Plasma Treated S1O2 Spin-On Glass
Authors: Park Min , Lee Joong Whan , Koo Jin Gun , Kim Kyung Soo , Yoo Hyung Joun , Nam Kee Soo , Jang Jin
Published: April 2011

We demonstrated that the quality of siloxane spin-on glass (SOG) films, widely used as interlevel planarization dielectrics, is improved significantly by curing in argon plasma. The wet etch rate of SOG film decreases with increasing plasma treatment temperature or treatment time, and is much lower than that cured in a furnace. Long-time plasma treatment reduces the density of silanols (Si-OH) and methyl (−CH3) group, which act as adsorption sites of water. The results were compared with those obtained from the N2O (or H2 ) plasma treated SOG films. The modification of the SOG film by Ar plasma is related to the radiation damage and the reconstruction of the atomic structure during the plasma exposure. The role of metastable Ar (Ar*) appears to be very important to improve the SOG film; SOG film is more relaxed by the energy released from the conversion of Ar* to Ar.
Synthesis And Characterization Of Fluorinated Poly(Arylethers): Organic Polymers For Ic Imd
Authors: Hendricks Neil H. , Lau Kreisler S. Y. , Smith Aaron R. , Wan W. Brad
Published: April 2011

Among the more promising approaches to minimizing capacitance in the multilevel interconnect of integrated circuits containing sub-half micron metal spacings is the development of organic polymers which exhibit high performance in key attributes such as thermal stability, low dielectric constant, and low moisture absorption coupled with high outgassing rates of what little moisture may be present. The use of such polymers as the intermetal dielectric can reduce power consumption and cross talk, while increasing signal propagation speed. While polyimides are the most extensively characterized polymer thin film dielectrics, and are in many cases suitable for the intermetal dielectrics in multichip modules, their tendency to absorb significant quantities of moisture, coupled with relatively slow outgas characteristics (presumably due to hydrogen bonding between water molecules and the carbonyls of the polyimide) constitute significant impediments to throughput in the fabrication of IC interconnects.

The search for alternative polymers which incorporate the “good” characteristics of polyimides while exhibiting improvements in electrical, moisture, and processing characteristics led us to the development of nominally 1 μm spin-on films derived from a family of noncarbonyl containing aromatic polyethers. Fluorinated poly(arylethers) based on decafluorobiphenyl exhibit thermal stability comparable to polyimides, from ten to forty times lower moisture absorption, dielectric constants in the mid-two's, and good retention of storage modulus above their glass transition temperatures. The precursor spin-on solutions, formulated in low toxicity organic solvents, exhibit excellent shelf life, and can be prepared with extremely low levels of metallic contamination. This paper describes the synthesis and both solution and film properties of this newly developed class of highly processible thermally stable polymers, first reported by Mercer, et. al. [1]. The characteristics of the polymers when spin-coated on silicon wafers is emphasized. Thermal and thermomechanical properties of nominally 10-25 μm free standing films are also described.
Polyimide Nanofoams For Low Dielectric Applications
Authors: Carter K. R. , Cha H. J. , Dipietro R. A. , Hawker C. J. , Hedrick J. L. , Labadie J. W. , Mcgrath J. E. , Russell T. P. , Sanchez M. I. , Swanson S. A. , Volksen W. , Yoon D. Y.
Published: April 2011

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term “nanofoam”. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block leaving pores the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials, were investigated as well as a number of thermally labile polymers. The foams were characterized by a variety of experiments including, TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.
Analytical Electron- and Atomic Force Microscopy Study of Multilayered Oxide Films Formedon Ce-DOPED Ni
Authors: Czerwinski F. , Szpunar J.A. , Smeltzer W.W.
Published: April 2011

Oxide films up to 200 nm thick were grown at high temperatures on Ni substrates implantedwith 2x1016 Ce ions/cm2. The surface morphology, microstructure and microchemistry were examined by AFM and TEM/STEM techniques. It has been found that the oxide films are composed of three well defined sublayers, with essentially different microstructure and Ce concentration. The outer layer is composed of NiO and CeO2 nanocrystals with a size less than 5 nm. The same two phases are also present within the middle layer, although the NiO grains are much larger in comparison to nano-sized CeO2. In addition, Ce segregation along the NiO grain boundaries is detected in this layer. The inner layer is the thickest one and is composed of pure NiO grains. Oxide films having such a complex structure are characterized by a very low diffusion rate for both metal and oxygen ions. Oxygen isotope experiments revealed that the diffusion processes within the oxide film are controlled by the Ce-rich layers.
Characterization of Electrodeposited Cobalt/Platinum(Ill) Ultrathin Films and Multilayers
Authors: Jyoko Y. , Kashiwabara S. , Hayashi Y.
Published: April 2011

Reflection electron microscopy (REM) studies of Co electrodeposition on Pt(111) singlecrystal surfaces under potential control have revealed a heteroepitaxial and simultaneous multinuclear multilayer growth in a range from several up to some ten monolayer coverages at room temperature. This growth process has been dependent upon the crystallization overpotential during electrodeposition. REM observations have also suggested the formation of an ordered CoPt3 alloy at the interface between the Pt/Co ultrathin bilayers grown epitaxially on Pt(111) surfaces. Auger and photoelectron spectroscopy experiments on the Pt/Co/Pt(111) system have confirmed a limited interdiffusion or interfacial alloying below the Pt overlayer leading to an induced magnetic moment on the Pt atoms. The Pt/Co interface exhibits electronic interface states of mainly Pt-5d character. Cross-sectional transmission electron microscopy (TEM) observations have provided the first direct experimental evidence for composition modulation across successive layers in a Pt/Co nanometer-multilayered structure prepared by electrodeposition.
High Resolution Sem Imaging of Multilayer Thin Films
Authors: Kingsley J. R. , Ward I. D. , Vitarelli J. P.
Published: April 2011

The high resolution capability of the JEOL JSM-890 In Lens Field Emission Scanning Electron Microscope (ILFESEM) is used for the routine determination of both film thicknesses and surface morphologies from a single sample. This single sample approach is possible because of the 0.7 nm resolution of the instrument, and the simple sample preparation. In many cases, the desired information can be obtained from a simple cleave of the sample.
Hyperfine Field and Electronic Structure in Fe/Co and Fe/Ni Multilayer Systems
Authors: Takahashi Manabu , Hu Xiao , Kawazoe Yoshiyuki
Published: April 2011

We investigate hyperfine field (Hhf) distributions and electronic structures in magnetic Fe5/Co5 and Fe5/Ni5 multilayer systems using the standard Green function KKR band structure calculation. For the Fe5/Ni5 system the Hhf at the interfacial Fe site is about 10kG smaller than that at the interior Fe site, however, system the Hhf are almost constant in Fe layer for the Fe5/Co5. At the interfacial Ni site the Hhf is almost twice as large as at the interior Ni site or in bulk fcc Ni. Valence contributions to the hyperfine fields (Hv) play important roles for the Hhf distributions. We discuss the relations between core contribution and local spin moment and between valence contribution and total moment within the 1st and 2nd nearest neighbor shells.
Stress, Microstructure, and Thermal Behavior in Mo/Si X-Ray Multilayers
Authors: Nguyen Tai D. , Underwood James H.
Published: April 2011

The relationship between intrinsic stress and microstructural evolution in nanometer Mo/Si multilayers deposited by magnetron sputtering at low working pressure (2.5 mTorr) is studied. The stress depends strongly on the microstructure which evolves with the multilayer period. In-situ thermal stress measurements show stress relaxation is observed in Mo/Si multilayers after annealing at 300°C in nitrogen ambient, due to microstructural changes in the multilayers. Average stress exhibits changes after annealing at 500°C which correspond to increased interdiffusion between the layer materials and crystallization at the interfaces.
X-Ray Optical Properties of C/C-Multilayers Prepared by Pulsed Laser Deposition (PLD)
Authors: Dietsch R. , Holz T. , Mai H. , Hopfe S. , Scholz R. , Wehner B. , Wendrock H.
Published: April 2011

The mass density of thin a-C films prepared by PLD is determined by the parameters of the ablation process. This fact results from various concentrations of sp3 and sp2 bounded atoms in the films, that are created for different laser power densities. Thus more diamondlike or more graphite-like layers are obtained. The alternate deposition of layers with different mass densities enables the preparation of C/C- multilayers that show X-ray optical activity. In the present investigations C/C-multilayers were deposited on silicon substrates at room temperature under UHV-conditions.

The double layer thickness d was changed in the range from 74Å through 18Å. High quality interfaces and very reproducible average d-spacing resulted in an energy resolution of 0.7% for 120 period stacks. Due to chemically almost equivalent layers the chemical driving forces of atomic transport in these multilayers vanish. Thus e.g. thermal stability is observed up to 700°C for an appropriate heat treatment. The limiting factor of thermal stability is caused by SiC-formation from reactions between layer stack and silicon substrate.

In-situ ellipsometry, grazing incidence x-ray diffraction, high resolution electron microscopy (HREM) and image processing were applied for specimen characterization.
AFM, XPS and XRD Studies of W Films Growth by Lpcvd Onto Tin Substrates
Authors: Santucci S. , Lozzi L. , Passacantando M. , Picozzi P. , Grifoni L. , Diamanti R. , Moccia G. , Alfonsetti R.
Published: April 2011

Thin films of W were grown using the low pressure chemical-vapour deposition technique in WF6/SiH4 flow on a TiN layer obtained by annealing in nitrogen atmosphere Ti films for different times. The investigation of W nucleation was followed by Atomic Force Microscopy in air. The Atomic Force images taken after fixed time of exposure of the TiN layer to the WF6/SiH4 flow show, on the surface of the W films, the presence of columnar structures only when the TiN films were obtained with forming times below 100 minutes. To investigate this effect X-ray Photoelectron Spectroscopy depth profile and X-Ray Diffraction measurements were performed on the obtained W/TiN films. The results show the deeper penetration of the nitrogen into the titanium layer with the longer forming time and a non stoichiometric composition of TiN interfacial layer which strongly influences the W nucleation.
In Situ Tem Study of Reactions in Iron/amorphous Carbon Layered Thin Films
Authors: Itoh Toshio , Sinclair Robert
Published: April 2011

Reactions between Fe and amorphous carbon (a-C) below 600ºC have been investigated. In situ annealing in a transmission electron microscopy (TEM) was performed on a-C/Fe/a-C trilayer films deposited by DC sputtering. As-deposited films showed a well defined tri-layered structure and an average Fe grain size of about 50Å. Cementite (Fe3C) grains appeared in the Fe layer by annealing around 300ºC. As the annealing temperature was raised, the number and size of the cementite grains increased. When the annealing temperature reached 500ºC, the Fe layer completely turned into cementite with an average grain size of 1000Å. At this point the film still kept a well defined tri-layered structure even though some parts of the cementitelayer agglomerated. Above 500ºC, the cementite layer started to “move” into the a-C leaving graphite behind. Graphite formed in this process is strongly textured with the (0002) graphite basal planes parallel to the surface of the moving cementite. This process is concluded to be carbide mediated crystallization of a-C, similar to silicide mediated crystallization of silicon in Ni-Si and Pd-Si systems.
Structural and Electrical Properties of Thin Metal Films Deposited at Low Temperature
Authors: He L. , Li E. , Morrison E. , Sirur D. , Shi Z. Q.
Published: April 2011

Thin metal layers play an important role in the development of electronic devices. The thin metal films deposited at low temperature (LT=77K) showed some unique properties which enhanced device performance. The micro-structural properties of thin metal films formed at room temperature (RT) and LT were investigated. An insulating substrate was used for Au, Pd Al and Ag metal deposition. The metal films were deposited by vacuum evaporation with thickness ranged from 100 Å to 100 Å. The surface morphology of the metal films was determined by transmission electron spectroscopy (TEM). The resistance of the films was insitu measured as a function of film thickness and temperature. Electrical measurement found that these films shown several orders lower resistance compared to the film obtained at room temperature at very thin thickness, which, implies potential application of these films on electronic and optoelectronic devices. It is found that the LT films showed much lower densities of grain boundaries than the RT samples. This is consistent with the resistivity measurement results.
Nanocrystalline Solutions as Precursors to The Spray Deposition of Cdte Thin Films
Authors: Pehnt Martin , Schulz Douglas L. , Curtis Calvin J. , Moutinho Helio R. , Swartzlander Amy , Ginley David S.
Published: April 2011

In this article we report the first nanoparticle-derived route to smooth, dense, phase-pure CdTe thin films. Capped CdTe nanoparticles were prepared by injection of a mixture of Cd(CH3)2, (n-C8H17)3 PTe and (n-C8H17)3P into (n-C8H17)3PO at elevated temperatures. The resultant nanoparticles 32-45 Å in diameter were characterized by x-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy, thermogravimetric analysis and energy dispersive x-ray spectroscopy. CdTe thin film deposition was accomplished by dissolving CdTe nanoparticles in butanol and then spraying the solution onto SnO2-coated glass substrates at variable susceptor temperatures. Smooth and dense CdTe thin films were obtained using growth temperatures approximately 200 °C less than conventional spray pyrolysis approaches. CdTe films were characterized by x-ray diffraction, UV-Vis spectroscopy, atomic force microscopy, and Auger electron spectroscopy. An increase in crystallinity and average grain size as determined by x-ray diffraction was noted as growth temperature was increased from 240 to 300 °C. This temperature dependence of film grain size was further confirmed by atomic force microscopy with no remnant nanocrystalline morphological features detected. UV-Vis characterization of the CdTe thin films revealed a gradual decrease of the band gap (i.e., elimination of nanocrystalline CdTe phase) as the growth temperature was increased with bulk CdTe optical properties observed for films grown at 300 °C.
Characterization of Multilayer Thin Film Structures for Gas Sensor Applications
Authors: Dibattista M. , Patel S. V. , Wise K. D. , Gland J. L. , Mansfield J. F. , Schwank J. W.
Published: April 2011

A nicrofabricated silicon-based chemical gas sensor with a discontinuous film of Pt / TiOx, as the active sensing component has been characterized by atomic force microscopy, environmental scanning electron microscopy, and transmission electron microscopy. A study of the device's multilayer structure and of the thin sensing film is undertaken to understand and control the sensing properties of the metal / semiconducting materials. The purpose of this research is to advance the understanding of the conduction mechanism and provide a basis for optimizing the sensing properties and microstructure of the sensing device.
Reactive Diffusion - Competition of Stable and Metastable Phases
Authors: Gusak Andrei M. , Nazarov Andrei V.
Published: April 2011

What happens as the interface of the initial virgin couple of materials at the very beginning of reactive diffusion?-composition changes, vacancy fluxes, stress generation, nucleation of intermediate phases and movement of newly born interphase interfaces. All these processes are closely interrelated and lead to formation and growth of certain phases andto suppression of others. We present the review of phase competition theory taking into account some of aforementioned factors and application of this theory to the description of solid state amorphizing reactions.

Nontraditional methods of producing the amorphous metallic alloys based on the solid state arnorphizing reactions have been developed during the last decade - amorphizing by diffusion, by ball milling, spontaneous vitrification and others. The main problem here from the theoretical point of view is to explain why doesthe metastable amorphous phase appears instead of stable intermediate phases with corresponding composition.
Study of Mechanical and Elastic Properties of Diamond Films by Surface Acoustic Wave Spectroscopy (SAWS)
Authors: Kuschnereit R. , Hess P.
Published: April 2011

The density and elastic properties of a 1.9 μm thick polycrystalline diamond film deposited on a silicon substrate were measured by surface acoustic wave (SAW) spectroscopy. A density of 3.45±0.05 g/cm3, Young's modulus of 940 ± 20 GPa and Poisson's ratio below 0.12 were determined from the dispersion of a broadband coherent surface acoustic wave pulse propagating in the layered system. The surface wave pulses were generated using a ns UV laser pulse and detected with a piezoelectric foil transducer.
Residual Stresses Analysis in Diamond Layers Deposited on Various Substrates
Authors: Rats D. , Bimbault L. , Vandenbulcke L. , Herbin R. , Badawi K. F.
Published: April 2011

A major problem for diamond coating applications is that diamond films tend to exhibit poor adherence on many. substrates and typically disbond at thicknesses of the order of few micrometers due especially to residual stresses. Residual stresses in diamond are composed of thermal expansion mismatch stresses and intrinsic stresses induced during film growth. Diamond films were deposited in a classical microwave plasma reactor from hydrocarbon-hydrogen-oxygen gas mixtures. Thermal stresses were directly calculated from Hook's law. On silicon substrate, intrinsic stresses were deduced by difference from measurements of total stresses either by the curvature method or by X-ray diffraction using the sin 2ψ method. These investigations allow us to discuss the origin of the intrinsic stresses. The residual stress level was also investigated by Raman spectroscopy as a function of the deposition conditions and substrate materials (SiO2, Si3N4, Si, SiC, WC-Co, Mo and Ti-6A1-4V). We show that the thermal stresses are often preponderant.
Adhesion Evaluation of CVD Diamond Films and Metal Reinforced Composite Diamond Films
Authors: Bahr D. F. , Nelson J..C. , Zhuang D. , Pfender E. , Heberlein J. , Gerberich W. W.
Published: April 2011

Poor adhesion of diamond films limits the use of CVD diamond films as coatings for cutting tools. The adhesion of these films is limited by stresses in the film caused by thermal expansion mismatch between the substrate and the film and by voids present at the interface due to the morphology of the crystal growth. A three step process of making diamond composite films has been developed, involving nucleation of individual diamonds on the substrate, electroplating a metal binder in the voids between the crystals, and lastly growing a complete film over the composite layer. The metal binder acts both to fill the voids at the interface and to absorb energy during fracture processes at the interface. Diamond growth was performed in a DC Triple Torch reactor using a mixture of methane and hydrogen with a molybdenum substrate. Measurements to determine the amount of improvement of the film adhesion have been performed. These tests include indentations using conventional hardness testing equipment and four point bend tests with the film in tension and compression. A correlation is shown between the plastic zone of the substrate and the area of the film which delaminated during indentation. Bend tests with the film in tension did not delaminate the film, instead the film underwent intergranular fracture. Bend tests in compression act similarly to pile up around an indentation, and cause film delamination. Residual stress measurements in the single step film show a compressive stress of 650 MPa.
Synthetic Diamond Strength Enhancement Through High Pressure/High Temperature Annealing
Authors: Jackson W. E. , Webb Steven W.
Published: April 2011

Annealing of low inclusion, single crystals of synthetic Type I diamond at 1200–1700°C and 50–60kbar, was observed to increase average crystal compressive fracture strength by as much as 20%. The increase in strength is associated with the healing of lattice dislocations, coalescence of small (< 400 nm) metal inclusions, and dissociation of aggregatenitrogen. Photoluminescence and FTIR spectroscopic data indicate H3 and “A”-type defect centers are unstable relative to NVx and “C”-type defect centers under the conditions of these experiments. Dissociation rate is greater in the (111) growth sector than in the (100). Changes in residual lattice strain of the samples could not be detected using Raman spectroscopy and optical microscopy. A model reaction of the type, 2V + N2V = NV2 + NV, in which N = nitrogen and V = vacancy (i.e., N2V = H3 center) is proposed which provides a qualitative thermodynamic understanding of the observations reported in this study consistent with previous results of other researchers. In addition, photoluminescence examination of smaller crystals produced from a quench of early stage non-equilibrium growth reveal a lower concentration of aggregate nitrogen than those quenched from late stage growth suggesting that nitrogen may aggregate via in situ annealing processes. Ultimately, understanding mechanisms to improve synthetic single crystal diamond strength will lead to improved tools which utilize such crystals (e.g., drill bits and saws for cutting stone and concrete) which constitute a market of ≈ $2b worldwide.
Processing-Microstructure-Tensile Property of Vapor Grown Carbon Fiber Reinforced Carbon Composite
Authors: Ting Jyh-Ming
Published: April 2011

In contrast to the form in which other carbon fibers are produced, vapor grown carbon fiber (VGCF) is produced from gas phase precursors in the form of individual fibers of discrete lengths. VGCF can be harvested as a mat of semi-aligned, semicontinuous fibers, with occasional fiber branching and curling. The use of VGCF mats as reinforcement result in composites which exhibit unique microstructure and physical properties that are not observed in other types of carbon composites. This paper describes the processing of VGCF mats reinforced carbon composites, and its unique microstructure and properties. Utilization of fiber tensile properties, as well as thermal conductivity, in the composites is discussed. Comparison of experimental results from various VGCF composites to theory indicates that mechanical properties are more strongly affected by characteristics of VGCF mat than are thermal conductivity. The implications of this relationship favors applications for thermal management where structural demands are less stringent.
Deposition of Diamond-Like Carbon Films by PECVD
Authors: Park Kyu Chang , Chun Soo Chul , Song Kyo Jun , Park Min , Oh Myung Hwan , Choi Seong Soo , Park Jung Hae , Yang In Sang , Jang Jin
Published: April 2011

We have studied the structural properties of hydrogenated carbon films deposited by plasma enhanced chemical vapor deposition (PECVD). The substrate holder in reaction chamber could be biased and be heated. The Raman peak intensity at 1350 cm−1 was increased by reducing CH4 flow rate. The film structure changed from soft a-C:H to hard carbon with decreasing CH4 flow rate, resulted from increased self-bias. The 1520 cm−1 peak shifts to higher frequency by reducing the CH4flow rate, probably resulted from the increased internal stress.
Effect of Microstructure in Metal Reinforced Composite CVD Diamond Films on Mechanical Properties
Authors: Hoehn J. W. , Bahr D. F. , Heberlein J. , Pfender E. , Gerberich W. W.
Published: April 2011

Comparison of behavior observed during deadhesion of CVD diamond films and compositional analysis of their microstructure allows a correlation between microstructure and mechanical behavior to be made. Diamond films were grown in a DC Triple Torch Reactor using a mixture of methane and hydrogen on molybdenum substrates. To address the issue of voids at the interface, a metal binder was electroplated after the nucleation of individual diamond crystals on the substrates. The films were completed by growing a layer of diamond upon the composite layer. Interfacial composition and structure of the films are characterized by a x-ray, Auger, and Raman spectroscopy. A carbide may act to enhance the adhesion via chemical bonding between the substrate and film. Diffusion of the binder into the substrate and film is also important for mechanical properties and is confirmed by x-ray mapping. It is suggested that a diamond like carbon layer acts to enhance the adhesion of the film to the substrate.
Diamond-Like Carbon Deposition for Tribological Applications at Los Alamos National Laboratory
Authors: Walter K. C. , Nastasi M. , Kung H. , Kodali P. , Munson C. , Henins I. , Wood B. P.
Published: April 2011

Diamond-like carbon (DLC) films have been deposited on silicon using two deposition techniques. Both deposition techniques used acetylene (C2H2) plasmas as the carbon/hydrogen source. One technique, that is relatively well known, employs an rf-plasma with an associated self-bias on the substrate. DLC films have also been deposited using a pulsed-bias method. Coatings of various thickness have been deposited using both deposition methods, and various combinations of gas pressure and bias. Coating characteristics, such as composition, density, and sp3 content, of selected films will be presented. For each deposition technique, the correlation between coating characteristics, mechanical properties and tribological behavior is presented.
Correlations Between the Substrate Temperature, Properties and Tribological Performance of Sputter-Deposited Amorphous Carbon Films
Authors: Mounier E. , Juliet P. , Quesnel E. , Pauleau Y. , Dubus M.
Published: April 2011

Amorphous carbon films have been deposited on various grounded substrates by direct current (DC) magnetron sputtering from a graphite target in an argon discharge. The argon pressure and sputtering power density were fixed at 0.25 Pa and 2.65 W cm−2, respectively. The substrate temperature was varied from 50 to 350°C. The hydrogen content determined by ERDA and the electrical resistivity of films were found to be dependent on the base pressure in the deposition chamber and substrate temperature. The mass density of films evaluated from RBS data and compressive residual stresses in the films decreased with increasing substrate temperature from 2.2 to 1.4 g cm−3 and - 0.6 to - 0.2 GPa, respectively. The friction coefficient and wear rate of about 2-μm-thick carbon films deposited on polished stainless steel disks were determined by alumina ball-on-disk tribological measurements conducted in dry air under a load of 4.9 N with a sliding velocity of 10 m min−1 for 105 cycles. The tribological performance of carbon-coated disks are correlated with the deposition temperature and physical characteristics of carbon films.
Simulation of Uniformity and Lifetime Effects in Collimated Sputtering
Authors: Taita R. N. , Dewb S. K. , Tsaic W. , Hodul D. , Brett M. J. , Smy T.
Published: April 2011

Collimated sputtering has been successful in providing good contact barriers for sub-half micron contacts with aspect ratios of 3 and greater. This approach does present drawbacks however, particularly in terms of reduced deposition rates and degraded film uniformity. The flux collected on the collimator leads to closing off of the cells, further reducing deposition rate on the wafer and limiting the life of the collimator. This paper demonstrates simulation of the filling of the collimator with different system configurations and pressures using the SIMSPUD vapor transport and SIMBAD thin film growth simulators. The model can determine collimator filling uniformity, blanket film uniformity, angular distribution of collimated sputter flux, and lifetime of the collimator. Given the target erosion profile, system geometry, and deposition rate, collimator lifetime can be predicted. The model indicates that for a 300 mm diameter source a drop in operating pressure from 0.67 Pa to 0.27 Pa has little effect on collimator life in terms of kWh, while increasing collimator life in terms of wafers by about 50%. The increase in the number of wafers processed comes at the expense of a small loss of uniformity.