bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of deposition and treatment conditions on growth of nanometer PtSi heterostructure
Authors: Wang Peilin , Yin Jinghua , Sheng Wenbin , Zheng Yufeng , Zhao Liancheng , Xu Daming
Published: July 2002

Under different substrate temperatures, deposition thickness, and annealing temperatures, the growth of nanometer-scale PtSi/p–Si(111) heterostructures prepared by sputtering was investigated by x-ray photoelectron spectrum (XPS), x-ray diffraction (XRD), and atomic force microscopy (AFM) techniques. The results of XPS show that the peaks of the Pt4f chemical binding energies of deposited Pt film specimens shift to higher energies after annealing. Pt, PtSi, and Pt2Si phases existing in the annealed film are verified by XRD. AFM observations prove that the surface morphologies are obviously different with different treatment conditions. The growth of the PtSi phase and the distribution of silicides are intensely affected by the deposition and technological parameters. It is also confirmed that Pt, PtSi, and Pt2Si phases coexist in the same layers. In the present study, the more uniform and flatter heterostructure film of PtSi/p–Si(111) is attained under the conditions with annealing temperature of 500 °C (30 min), substrate of 300 °C, and 5 nm Pt.
Atomic force microscopy of reaction of ammonia gas with crystalline substituted benzoic acid
Authors: Zeng Qingdao , Wang Chen , Bai Chunli , Li Yan , Yan Xinjian
Published: July 2002

Regular nanostructures are formed by chemical reaction of ammonia gas with crystalline substituted benzoic acid such as p-bromobenzoic (1a), p-toluic (1b), p-aminobenzoic (1c), and p-nitrobenzoic acid (1d). Their size and shape are determined and depicted by atomic force microscopy (AFM). AFM reveals that the crystal main face (100) of 1a, (100) of 1b, (100) of 1c, and (001) of 1d exhibits craters and volcanoes, craters and volcanoes, volcanoes, and volcanoes, respectively, whereas the long side face (100) of 1d gives rise to craters and volcanoes. All the experimental results are correlated with the crystal structures. Molecular interpretations of the AFM features of 1a, 1b, 1c, and 1d are given.
Importance of Arc Gap Control in Vacuum Consumable Arc Remelting of Superalloys
Authors: Mumau G. R. , Aufderhaar W. B.
Published: July 2002

In vacuum consumable arc remelting, control over the ingot solidification rate is of paramount importance to optimum product quality. In general, solidification rate is very dependent upon ingot size and melting current which help to define the general characteristics of the molten pool geometry and that of the advancing freezing front within the ingot. However, control of these parameters is achieved by precisely monitoring arc gap throughout the melting operation. By having a close control over the arc gap, the vacuum melter can eliminate variations in solidification rate which can cause localized harmful segregates. There are several types of controls used in the vacuum melting industry today and these are discussed, including the hash control used at Special Metals Corporation. The important features of the control are outlined with respect to their influence on arc gap, including speed of feed, voltage limitation, and basic hash/arc gap relationships. The importance of controlling the arc gap in Udimet 718 is shown by illustrating the effect of intentional controlled variations in arc gap at several melting currents on the formation of several types of segregates. The method of programming arc melt cycles to gain the most control over arc gap to ensure a reproducible, high quality product is discussed.
The Effect of C and N on the Properties of Fe–Cr–Mo Ferritic Stainless Steels
Authors: Bond A. P. , Steigerwald R. F.
Published: July 2002

The effect that C and N contents have on the toughness of Fe–Cr–Mo alloys has been known for some time, but only recently have vacuum melting and inert-gas or inert-gas-vacuum combination refining process between developed to the point where low interstitial ferritic stainless steels are commercially attractive engineering materials. This paper reviews the effects of C and N contents on various properties of Fe–Cr–Mo alloys in which the interstitial level varies over the range 50–1000 ppm. The alloys are divided into two classes: 25Cr–Mo and 18Cr–Mo. The properties studied included toughness, welded ductility, resistance to intergranular corrosion, and resistance to pitting corrosion. Some of the higher Mo alloys presented interesting problems since heat treatments used to negate the effects of carbide and nitride precipitation produced undesirable phases. This problem could be avoided in the higher purity alloys by using high temperature annealing treatments. The amount of C and N that can be tolerated before these ferritic stainless steels become susceptible to intergranular corrosion after welding is a function of their Mo and Cr contents with the more highly alloyed material having the higher limits. Both Ti and Nb can be used to stabilize less pure steels against intergranular corrosion, but both C and N must be considered in determining the proper addition. Although stabilizing additions appear to improve the as-welded ductility of less pure Fe-Cr-Mo alloys, they do not improve their annealed toughness. Generally speaking, purer alloys have better resistance to pitting corrosion.
Effect of back contact on field emission from carbon films deposited by very high frequency chemical vapor deposition
Authors: Kosarev A. I. , Andronov A. N. , Vinogradov A. J. , Felter T. E. , Titkov A. N. , Makarenko I. V. , Vaqar M. Z. , Robozerov S. V. , Shutov M. V.
Published: July 2002

The effect of material and surface morphology of the back contact on field emission has been studied in carbon films deposited by very high frequency chemical vapor deposition at low temperature. The emission current was measured as a function of applied field for carbon films deposited simultaneously on various substrates coated with metals having different work functions (Ti, Cu, Ni, and Pt). Different metals demonstrated different types of microstructure and surface morphology. Therefore, the effect of back contact morphology was especially studied. The material of the back contact influenced the emission properties, but no direct correlation between emission and the work function of metal was observed. The field emission threshold was found to be affected by the roughness of the back contact: a Ti contact with 270 nm roughness showed emission threshold of Eth=3 V/μm, while a contact made of the same material, but with roughness of ∼2.5 nm had Eth=13 V/μm.
Built-in electric fields in GaAs/GaAs structures with different in situ substrate treatments
Authors: Luyo-Alvarado Javier , Meléndez-Lira Miguel , López-López Máximo , Goto Shigeo
Published: July 2002

We have prepared GaAs substrates prior to molecular beam epitaxial growth by the following in situ treatments: (1) The usual thermal cleaning under an arsenic flux, (2) cleaning by hydrogen radicals (H*), and (3) exposure to trisdimethylaminoarsine (TDMAAs). The effects of these treatments on the optical properties and built-in electric fields in GaAs/GaAs structures were studied. In order to investigate the effects of the substrate type on the properties of the GaAs epilayers, undoped semi-insulating (SI) GaAs (100) and Si-doped n+-GaAs(100) substrates were used. Reflection high-energy electron diffraction during the growth, and atomic force microscopy in air showed that the smoothest surface morphology was obtained for the layer grown on a H*-cleaned SI substrate at 570 °C. For Si-doped substrates the smoothest layer was obtained on a TDMAAs-treated substrate. The concentrations of interfacial residual impurities of C and O were measured by secondary ion mass spectroscopy (SIMS). For SI substrates, the usual thermal cleaning process resulted in very high concentrations of C (2×1019 atoms/cm3) and O (1.3×1018 atoms/cm3) at the interface. The impurities were drastically diminished to below the SIMS detection limit by using H*-cleaning. We observed higher concentrations of impurities on Si-doped substrates. Internal electric fields due to the interfacial impurities were detected by the presence of Franz–Keldysh oscillations in the room temperature photoreflectance spectra. The samples with the highest amount of interfacial impurities presented the strongest internal electric fields. Photoluminescence results showed a clear correlation between the amount of interfacial impurities and signal intensity, the lower the impurity content the stronger the photoluminescence intensity. The signal associated with carbon impurities dominates the photoluminescence spectra for GaAs layers grown on SI substrates, while for samples grown on Si-doped substrates the signal coming from the substrate is the dominant one.
Sidewall oxidation behavior of dichlorosilane-based W-polycide gate
Authors: Kim Hyeon-Soo , Lee Sang-Moo , Yeo In-Seok , Lee Sang-Do , Pyi Seung-Ho
Published: July 2002

We studied the sidewall oxidation behavior of dichlorosilane-based WSix/P-doped Si stack gate electrode and compared to that of monosilane-based WSix. WSix was known to be abnormally oxidized during reoxidation after gate stack patterning, resulting in deformation of the sidewall profile of gate electrode. We found that low temperature oxide for mask of gate patterning was effective to prevent the abnormal oxidation. Preannealing at temperature higher than 800 °C was also found to effectively suppress the abnormal oxidation of crystalline WSix.
Epitaxial VN(001) Grown and Analyzed In situ by XPS and UPS. I. Analysis of As-deposited Layers
Authors: Haasch R. T. , Lee T. -Y. , Gall D. , Greene J. E. , Petrov I.
Published: July 2002

X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS) were used to characterize as-deposited epitaxial VN(001) layers grown in situ. The films were deposited on MgO(001) at 650 °C in pure N2 discharges maintained at a pressure of 5 mTorr (0.67 Pa). Mg Kα and monochromatic Al Kα x-ray sources were used to generate the XPS spectra, while the UPS data were generated by He I and He II UV radiation. Analysis of the results show that the VN(001) surfaces are free of O and C. The films were found to be stoichiometric in agreement with Rutherford backscattering spectroscopy (RBS) results, yielding a N/V ratio of 1.06±0.02.
Chemical beam epitaxy growth of self-assembled InAs/InP quantum dots
Authors: Poole P. J. , McCaffrey J. , Williams R. L. , Lefebvre J. , Chithrani D.
Published: July 2002

We have used transmission electron microscopy and low temperature photoluminescence to study the growth by chemical beam epitaxy of self-assembled InAs/InP quantum dots as a function of growth interruption time. As the deposited InAs layer is given time to migrate on the semiconductor surface a number of different features appear. The InAs layer first forms a rough quantum well with monolayer fluctuations in width before forming elongated InAs islands. These islands are elongated along the [01-1] direction due to surface diffusion dynamics. These then break up into individual quantum dots, and slowly increase in height. These dots are found to be approximately square with their sides aligned along the 〈100〉 directions and lateral dimensions of 30–40 nm.
What causes the broad modulation in the x-ray reflectivity curve?
Authors: Xu Ming , Yang Ning , Yu Wenxue , Xiong Gang , Liu Cuixiu , Chai Chunlin , Luo Guangming , Mai Zhenhong , Lai Wuyan
Published: July 2002

In contrast to the general view that the broad modulation in the reflectivity curve of multilayers is correlated to the oxide cap layer, we show that it is usually the buffer layer that cause the broad modulation in x-ray reflectivity curve. The buffer layer thickness can be exactly and directly determined from the broad modulation by a modified Bragg’s law. Furthermore, we theoretically analyze the effect of the cap layer on the broad modulation.
Impact of nanometer-scale roughness on contact-angle hysteresis and globulin adsorption
Authors: Müller Bert , Riedel Marco , Michel Roger , De Paul Susan M. , Hofer Rolf , Heger Dietmar , Grützmacher Detlev
Published: July 2002

Besides surface chemistry, the surface roughness on the micrometer scale is known to dominate the wetting behavior and the biocompatiblity properties of solid-state materials. The significance of topographic features with nanometer size, however, has yet to be demonstrated. Our approach is based on well-defined Ge nanopyramids naturally grown on Si(001) using ultrahigh vacuum chemical vapor deposition, where the nanopyramid density can be precisely controlled by the growth conditions. Since the geometry of the nanopyramids, often termed dome clusters, is known, the surface roughness can be characterized by the Wenzel ratio with previously unattainable precision. Dynamic contact-angle measurements and adsorption of γ-globulin as a function of that ratio demonstrate the strong correlation between surface nanoarchitecture, on one hand, and wetting behavior and biocompatibility, on the other hand. Related x-ray photoelectron spectroscopy measurements reveal that potential changes of surface composition can be definitely excluded.
Low temperature polysilicon chemical vapor deposition system for thin film transistor liquid crystal diode
Authors: Hosokawa Akihiro , Shang Q. , Kardokus J. , Blonigan W.
Published: July 2002

Polysilicon thin film transistor (TFT)-based displays are increasingly found in cell phones, mobile communicators, PDAs, portable DVD players, and mobile computers because they have high resolution and low power consumption. The AKT plasma-enhanced chemical vapor deposition system made by Applied Materials is used to deposit multilayer dielectric films including precursor low-hydrogen-content amorphous silicon for manufacturing these displays. The polysilicon film is converted from an amorphous precursor film by an excimer laser annealing process. Production of a good quality polysilicon precursor film requires that the hydrogen content of the film be controlled below 2%. Achieving low hydrogen content requires uniform treatment at high temperature (500±10 °C) after deposition. This article describes the design and performance of the large, high temperature heat chamber integrated in a cluster-tool-based deposition system for both preheat and postannealing of the substrate. [Q. Shang, J. K. Kardokus, and A. Hosokawa, U.S. patent pending (Dec. 2000).]
Formation of Hf ohmic contacts by surface treatment of n-GaN in KOH solutions
Authors: Chung Ming-Shaw , Lin Wen-Tai , Gong J. R.
Published: July 2002

Effects of surface treatment of n-GaN on the formation of Hf ohmic contacts as a function of the chemical solutions and immersion time are studied. Hf ohmic contacts to n-GaN were readily formed without postdeposition annealing by surface treatment of n-GaN films in a KOH solution at 70 °C for 60 min prior to Hf deposition. The specific contact resistance as low as 7.5×10−5 Ω cm2 can be reached. X-ray photoelectron spectroscopy investigation showed that the oxide and carbon contaminants present on the surface of n-GaN could be substantially removed by treatment in the 70 °C KOH solution for 60 min, resulting in the formation of Hf ohmic contacts to n-GaN without postdeposition annealing. For improving the formation of ohmic contacts to n-GaN the performance of surface treatment of n-GaN in the 70 °C KOH solution is superior to that in the commonly used HF and HCl solutions.
Fabrication and characterization of C implantation standards for Si1−x−yGexCy alloys
Authors: Laursen T. , Chandrasekhar D. , Hervig R. L. , Mayer J. W. , Smith David J. , Jasper C.
Published: July 2002

Known amounts of carbon were implanted into a set of Si1−xGex alloy films (0<x<0.35) to provide quantification standards for C composition measurements of Si1−x−yGexCy alloys by secondary ion mass spectrometry. The implanted doses were fixed to within ±2%, the thicknesses of implanted films were measured to within ±1% using high-resolution electron microscopy, and the Ge concentrations were determined to within ±0.5% using Rutherford backscattering spectroscopy. For Si:Ge ratios in the range Si66Ge34 to Si91Ge9, the relative sensitivity factor for carbon with respect to silicon, and for carbon relative to germanium, both decreased substantially with increasing Ge content.
Chemically dependent traps and polytypes at Pt/Ti contacts to 4H and 6H–SiC
Authors: Tumakha S. , Brillson L. J. , Jessen G. H. , Okojie R. S. , Lukco D. , Zhang M. , Pirouz P.
Published: July 2002

We have used low energy electron-excited nanoluminescence (LEEN) spectroscopy and x-ray photoemission spectroscopy (XPS) to probe deep level defect states at interfaces of 4H and 6H–SiC with Ti/Pt metallization. These studies aim to identify process conditions under which thermally stable ohmic and Schottky contacts can be obtained on SiC while minimizing the formation of deep level electronic states. Depth-dependent LEEN measurements establish the presence of localized states and their spatial distribution on a nanometer scale. Spectra from the near interface region of 6H–SiC indicate the existence of a SiC polytype with a higher band gap of ∼3.4 eV. Excitation of the intimate metal–SiC interface reveals a process-dependent discrete state deep within the SiC band gap. XPS measurements reveal consistent differences in the C 1s chemical bonding changes with specific process steps. Analogous chemical treatments of 4H–SiC also produce a lower band gap SiC polytype with ∼2.5 eV energy extending tens of nanometers beyond the interface—confirmed by transmission electron microscopy. This work is the first to show the effect of metal–semiconductor interactions not only on localized states but also on the lattice structure of the semiconductor near the interface.
Fluorine and boron co-doped diamond-like carbon films deposited by pulsed glow discharge plasma immersion ion processing
Authors: He Xiao-Ming , Hakovirta M. , Peters A. M. , Taylor B. , Nastasi M.
Published: July 2002

Fluorine (F) and boron (B) co-doped diamond-like carbon (FB-DLC) films were prepared on different substrates by the plasma immersion ion processing (PIIP) technique. A pulse glow discharge plasma was used for the PIIP deposition and was produced at a pressure of 1.33 Pa from acetylene (C2H2), diborane (B2H6), and hexafluoroethane (C2F6) gas. Films of FB-DLC were deposited with different chemical compositions by varying the flow ratios of the C2H2, B2H6, and C2F6 source gases. The incorporation of B2H6 and C2F6 into PIIP deposited DLC resulted in the formation of F–C and B–C hybridized bonding structures. The levels of the F and B concentrations effected the chemical bonding and the physical properties as was evident from the changes observed in density, hardness, stress, friction coefficient, and contact angle of water on films. Compared to B-doped or F-doped DLC films, the F and B co-doping of DLC during PIIP deposition resulted in the formation of films that possessed a reduced hydrogen concentration and stress, while maintaining a high hardness, low friction coefficient, and high wetting contact angle.
Transience of plasma surface modification as an adhesion promoter for polychlorotrifluorethylene
Authors: Subrahmanyan S. , Dillard J. G. , Love B. J. , Romand M. , Charbonnier M.
Published: July 2002

Poly(chlorotrifluoroethylene) (PCTFE) and other fluoropolymers are increasingly used as inner layer dielectrics. However, these polymers have low surface energies and correspondingly poor adhesive properties. Results are presented on the use of a low-pressure ammonia plasma to enhance the surface bondability of PCTFE. The plasma modified PCTFE film surfaces were characterized by x-ray photoelectron spectroscopy and contact angle measurements. Surface modified films exhibited improved adhesion to electroless copper deposits (180° peel test) compared to coated PCTFE controls and that underwent no plasma exposure. Annealing studies were conducted between 30 and 100 °C to examine the stability of the plasma-modified surfaces. For samples annealed below Tg, contact angle measurements indicated that the plasma-introduced groups remained bound on the surface for four weeks. For specimens annealed above Tg, the surface functionalities were absorbed within the bulk and surface rearrangement occurred within 10 h of annealing time. As a result of rearrangement, the benefit of adhesion enhancement by plasma is lost and the adhesion to copper is reduced.
Structure and Annealing Behavior of Metal Films Deposited on Substrates near 80 °K: I. Copper Films on Glass
Authors: Vook R. W. , Witt F.
Published: July 2002

An in situ x-ray investigation of copper films has been carried out. Films were deposited on glass at 80 °K and room temperature in high vacuum. Measurements were made on the as-deposited films as well as after annealing at temperatures up to 200 °C. Values for the stacking fault and twin fault densities, particle sizes, and strain in these films have been obtained. The presence of preferred orientations and grain growth during annealing was also studied.
Comparison of Auger electron spectroscopy, Auger electron appearance-potential spectroscopy, and disappearance-potential spectroscopy in a cylindrical-mirror-analyzer system
Authors: Kirschner J. , Losch W.
Published: July 2002

We describe a few modifications of a commercial CMA which allow us to complement Auger spectroscopy (AES) by two independent threshold spectroscopies: Auger electron appearance-potential spectroscopy (AEAPS) and disappearance-potential spectroscopy (DAPS). After establishing comparable conditions for AES and AEAPS, the signal-to-noise ratios are compared. AEAPS is found to be slightly more sensitive for Ti (factor of 2), much more for La (factor of 30), and much less for oxygen (factor of 0.02) than AES. Due to the small number of lines in the threshold spectroscopies and little line overlap, it is possible to detect minor constituents in multicomponent samples which cannot be found by AES. This is demonstrated for a stainless-steel alloy. DAPS has pronounced surface sensitivity, but a lower signal-to-noise ratio compared to AEAPS (a factor of 6 was determined for Ti). The differences in the depth of information of DAPS and AEAPS allow us to detect surface enrichment in alloys or preferential sputtering by ion bombardment without any further treatment of the sample. This is demonstrated for a Cr-16 Fe-84 alloy.
Uncarburized thoriated tungsten filament activation
Authors: Edwards D.
Published: July 2002

Reactivation of contaminated uncarburizeed thoriated tungsten filaments is accomplished repeatedly by sputtering with ∠300-eV argon ions.(AIP)
Double helix vacuum resistance heater
Authors: Patrick Raymond C.
Published: July 2002

A tantalum resistance heater with a unique double helix element which provides improved thermomechanical stability and temperature uniformity at high temperatures is described.(AIP)
Argon plasma bridge neutralizer operation with a 10-cm-beam-diameter ion etching source
Authors: Reader Paul D. , White Dennis P. , Isaacson Gerald C.
Published: July 2002

The plasma bridge neutralizer operating on argon offers a long-life, contamination-free method of neutralizing the ion beams of industrial etching and deposition sources. The neutralizer described herein is capable of neutralizing the 200-mA beam produced by the 10-cm-diameter ion source used for these tests. Beam plasma potential and electron temperature are essentially the same as those from an immersed thermionic emitter neutralizer. Lifetimes 3 to 5 times as great as immersed wires were obtained with the plasma bridge neutralizer in similar reactive environments.
Thin-film NiCr resistor
Authors: Buczek D. M.
Published: July 2002

Reactively evaporated NiCr resistors have been produced with slightly negative temperature coefficients of resistance. Evidence from the transmission electron microscope and Auger electron microprobe show these to be cermet structures with multiple conduction mechanisms. A theoretical model initially proposed by Neugebauer for discontinuous films is applied to these thin-film structures and expanded for the multiple conduction mechanisms and effect of expansion mismatch between the substrate and film.
Initial oxidation and oxide/semiconductor interface formation on GaAs
Authors: Wilmsen C. W. , Kee R. W. , Geib K. M.
Published: July 2002

Evolution of the oxide/GaAs interface formation for both thermal and anodic oxides is presented. This is accomplished by examining ESCA profiles of 21–85 Å thick thermal and anodic oxides. The anodic oxide begins with a nucleation and growth process during which the As oxides are leached out leaving a continuous layer of Ga2O3. Oxide growth then proceeds by Ga and As diffusion to the surface where they oxidize leaving the inner layer of Ga2O3 unchanged. Thus the anodic oxide/GaAs interface is formed during the first 40 Å of oxide growth. During thermal oxidation both Ga2O3 and As2O3 are formed but the As2O3 evaporates rapidly leaving the Ga2O3. Once the Ga2O3 layer is formed, the As is excluded from entering the continuous Ga2O3 layer and collects at the oxide/GaAs interface. This occurs after about 40 Å of oxide growth.
Pattern profile control utilizing shadowing effect in oblique ion-beam etching
Authors: Gokan H. , Esho S.
Published: July 2002

A new pattern profile control technique utilizing an ion-beam shadowing effect has been developed. A tapered sidewall is obtained by oblique ion-beam etching with a sublayer deposition on a layer to be etched before or after photolithography. Metal or photoresist can be used as a sublayer. Tapered pattern angle is controlled mainly by varying ion-bean angle and initial mask thickness. Sublayer thickness is chosen to eliminate discontinuous sidewall formation arising from an ion-beam shadowing effect. Since the chemical etching process can be completely eliminated in these processing steps, pattern profiles for all the materials are easily controlled with good reproducibility.
Artifacts observed during Auger profiling of Ta, Ti, and W metals, nitrides and oxynitrides
Authors: Ingrey S. , Johnson M. B. , Streater R. W. , Sproule G. I.
Published: July 2002

Studies of CKVV Auger spectra indicate carbide formation in certain metals and compounds resulting from ion beam bombardment of contaminated (air exposed) surfaces. Carbide buildup on W, Ta, and Ti surfaces after ’’static’’ sputter cleaning in an AES system, occurred in the presence of small partial pressures of CH4 generated from the speciman chamber walls and ion pump well. This carbide buildup was greatly accelerated by electron beam irradiation.
A new high repetition rate shutter to obtain short molecular beam pulses
Authors: Wolterbeek L. , Hofstra J. , Nijhof C.
Published: July 2002

This new shutter simply consists of a chopper wheel rotating a mere half-millimeter away from the skimmer-shaped diaphragm, which separates the source chamber from the flight tube. The repetition rate can be up to 104 pulses per s (width∼60 μs), at an intensity of ∼1019 molecules/sr s, whereas existing designs yield ∼1022 molecules/sr s, but only at a rate of 1 pulse per 1–10 s. Our design has two main advantages: since there is no gas valve, cumbersome electromechanical devices with large current pulses can be avoided. Second, one is now free to choose the nozzle parameters (e.g., p0, T0 and the throat diameter dn). The beam parameters were determined by means of an electron impact detector featuring a high efficiency ionizer, thus improving the signal-to-noise ratio.
Alternate method to fabricate doped hydrogenated amorphous silicon film
Authors: Huang F. S. , Wang Y. Y.
Published: July 2002

The doping effect was studied on hydrogenated amorphous silicon (a-Si:H) film. The specimens were deposited by rf sputtering. Various doped silicon wafers were used as targets. Instead of feeding PH3 or B2H6 gases to the system, the target acted as a dopant source. From conductivity measurements, we observed the phosphorus doping, whereas the p-type doping effect was hardly found. The current–voltage measurement shows field dependence and Ohmic relation in 100 and 300 K, respectively. We used different targets to fabricate n–p junction. The rectification appeared in current–voltage characteristics. The n–p junction also had photoresponse.
Preparation and analysis of carbon foils implanted with 100 μCi cm−2 of tritium
Authors: Timberlake J. , Kerst R. , Causey R. , Cohen S. , Fennimore J. , Manos D. , Strachan J.
Published: July 2002

The approaching use of tritium in tokamaks necessitates precursory studies to assess safety and handling, to ready diagnostics of T in plasmas, and to study T–H exchange, loss of T from solids, and T transport. To aid these efforts, eight carbon foils 12.7×1.25 cm were implanted in a linear plasma device with ions from hydrogen plasma containing 10−3 fraction of T. These foils will be used in future PLT plasma experiments. Experimental guidelines are: low activity, high safety, and sufficient T for detection. Incident ion energies and total fluxes yielded deposits of ∼100 μCi cm−2 (2×1015 cm−2) of tritium. Using autoradiography, we find that variations of ≲20% of an average concentration of 100 μCi cm−2 of T can be detected. Areas of <1 mm2 can be examined by the use of densitometry, thus providing a nondestructive method of analyzing surface distribution. Absolute calibrations were made by the measurement of tritium in one of the foils using carbon dissolution and scintillation counting techniques, while relative tritium concentrations were measured using an electron multiplier. Enhanced tritium deposition, attributed to plasma arcs, was observed on one of the foils.
Characterization of the surface net and electronic structure of AuGa2(001)
Authors: Nelson Jeffrey G. , Lince Jeffrey R. , Gignac William J. , Williams R. Stanley
Published: July 2002

The (001) face of the stoichiometric intermetallic compound AuGa2 has been studied for the first time using Auger electron spectroscopy, low energy electron diffraction, and electron energy loss spectroscopy. The argon ion bombarded and annealed surface is primarily Ga terminated, and structurally is comprised of two perpendicular domains which are based on a ((2)1/2×(18)1/2 )R45 unit cell. Bulk and surface plasmon loss features were observed at 15.6 and 10.4 eV, respectively. Loss features were also observed for the valence band and Ga 3d quasiparticle transitions.
An Auger/SEM study of the corrosion of β-brass alloyed with tin
Authors: Bevolo A. J. , Baikerikar K. G. , Hansen R. S.
Published: July 2002

Two brass samples, Cu56Zn44 and Cu56Zn43Sn1, were exposed to deaerated aqueous solution with composition 1 M NaCl+0.01 M HCl. Auger analysis of the Sn alloyed brass did not reveal any Sn surface segregation which eliminated a surface Sn passivating layer as a mechanism for the reduced corrosion rate in the Sn alloy. Auger depth profiles of the 1% Sn alloy revealed a pure copper layer separated from the bulk brass by a tin rich layer. SEM micrographs showed a porous, loosely adherent copper layer whose top surface retained the original polished finish, indicating little copper dissolution or redeposition. Our results suggest that the remaining copper is forced by the high void concentration into a porous layer whose thickness increases until a tin layer is formed, at the copper/brass interface, that separates the reactants and, thereby, retards the corrosive attack.
Properties and applications of diamondlike carbon films
Authors: Aisenberg S.
Published: July 2002

An ion beam deposition system has been used to deposit thin films of carbon with many diamondlike properties [S. Aisenberg and R. Chabot, J. Appl. Phys. 42, 2953 (1971)] which were subsequently confirmed by others [E.G. Spencer, P. H. Schmidt, P. C. Joy, and F. J. Sansalone, Appl. Phys. Lett. 29, 118 (1976)]. Included among properties are transparency, chemical inertness, strong substrate adhesion, high index of refraction, low optical loss over a wide spectra range (visible up to 40 mμ), and with resistivities ranging from 109 to 1016 Ω cm. The films have been observed by SEM to be much smoother than the substrates. An explanation of this effect is that the free surface energy of the mobile surface atoms is much higher (over an order of magnitude) than of liquid metals. The higher free surface energy (erg/cm2 or surface tension in dyne/cm) of the nonequilibrium surface atoms provides a stronger driving force towards minimum surface energy and minimum area and very smooth surface. One interesting application of this diamondlike carbon deposition process is hermetic barrier coatings on optical fibers (to reduce loss of strength with time normally due to water vapor and stress corrosion) and on suboptical memory disks, to give longer archive lifetimes.
Accelerated ion doping in Si MBE
Authors: Ota Yusuke
Published: July 2002

Silicon epitaxial layers have been grown with virtually any doping profile by combining molecular beam epitaxial growth with simultaneous low energy ion doping (ion doped Si MBE). Arsenic ions (As+) for n-type doping and boron ions (B+ or BR+2) for p-type doping accelerated to energies between 400 and 800 eV have shown a high sticking coefficient on the heated silicon surface, and it was found that the resulting films were bulklike if the growth temperature was high enough to anneal out the ion damages. In this paper, the basic design of the ion doped Si MBE system and the characteristics of the MBE films will be reviewed.
Additive thin film technology for hybrid circuit fabrication
Authors: Krokoszinski H.-J. , Oetzmann H. , Gernoth H. , Schmidt C.
Published: July 2002

Thin film hybrid circuits usually are fabricated by photolithographic structuring of an evaporated or sputtered metal layer sequence (substractive technology). In contrast to this, we discuss the abilities of ‘‘evaporation masking,’’ i.e., evaporation through metal masks (additive technology). Its main advantage is the local deposition of several different materials (conducting, resistive, semiconducting, insulating, electroluminescent, etc.) enabling the production of multilayer thin film devices. In this work we emphasize the possibility of producing complex hybrid circuits in one vacuum cycle including local insulations for capacitors, crossovers, and passivating oxide layers. Moreover, we discuss the equipment used, the electrical properties of some standard materials (NiCr, Al, Al2O3, etc.) and the resulting design rules for the hybrid layout. As a typical example, a thin film hybrid circuit on 2×2 in. glazed ceramics is presented which includes 800 crossovers, 56 thin film resistors, and 3 evaporated capacitors.
Behavior of plasma-sprayed TiC coatings under electron beam thermal shocks
Authors: Brunet C. , Dallaire S. , St-Jacques R. G.
Published: July 2002

Within the framework of a research program on materials for fusion machine, plasma-sprayed TiC coatings over Inconel 625 substrates were investigated. In order to evaluate the potential of these coatings in fusion environment, the existing thermal flux conditions on limiters of tokamaks are simulated with an electron beam thermal shock experiment. TiC coatings sprayed in air show severe damages when exposed to 2.5  kW  cm−2, 1.0  s, heat pulses. Coatings sprayed in an inert gas enclosure withstood 3.0 kW cm−2, 1.0 s, heat pulses without melting. Surface melting and subsurface crystal growth are observed in the case of coatings sprayed in air.
A quantitative appraisal of the backstreaming of forepump oil vapor
Authors: Lewin G.
Published: July 2002

If a vacuum vessel is evacuated with the forepump alone for some time, oil will be deposited on the vessel walls. Therefore, it is recommended to switch over from the roughing pump to the high vacuum pump as soon as possible. The effect of the pertinent parameters is calculated to obtain quantitative information. It is found that it is essential to remain in the viscous flow range and that this requirement is met, when the product of nitrogen (or air) pressure and tube inside diameter is at least 50 Pa cm. In addition, venting to atmospheric pressure is necessary during prolonged stand-by periods.
The use of anhydrous WO3 layers to record the position of 5–15 keV H+2 beams
Authors: Walck Scott , Buonaquisti A. D.
Published: July 2002

This note reports the use of anhydrous WO(3) powderr as a medium which can record the position of the 5−15 keV hydrogen ion beams. The process is quick v ersatile and simple. Beam position can be determined directly without need for chemical processing or extensive specimen preparation. The technique is recomm ended for those applications in which line of sight cannot be used to detect bea m position. (AIP)
Comparison of glow discharge cleaning and ion-impact desorption of stainless steel
Authors: Ruzic D. N. , Gerdin G. A. , Loxton C. M.
Published: July 2002

The effects of glow discharge cleaning (GDC) and ion-impact desorption (IID) of impurities on 302 stainless steel were compared using Auger electron spectroscopy (AES). Hydrogen GDC was done in a chamber attached to the Auger microprobe allowing transfer in vacuo to lessen recontamination. GDC removed the surface hydrocarbon layer, but deposited many constituents of the cathode and surrounding areas onto the sample. It also induced a high concentration of carbon which extended beyond the surface layer. The extent of the carbon layer varied with the prior treatment of the surface. IID is shown to maintain a higher surface purity. The feasibility of helium IID as an after-opening or between-shot cleaning technique for magnetic fusion experiments is discussed.
The influence of impurity and particle control on Tandem Mirror Experiment Upgrade plasma operation
Authors: Allen S. L. , Yu T. L. , Foote J. H. , Pickles W. L.
Published: July 2002

A variety of techniques are used in Tandem Mirror Experiment-Upgrade (TMX-U) to control impurities and reflux: repeated plasma pulses, glow discharge cleaning (GDC), and gettering. We performed a series of experiments under three different plasma-wall conditions: no wall conditioning after a machine maintenance cycle, glow-discharge-cleaned wall, and a gettered wall. We used several plasma diagnostics to determine the effect of these procedures on TMX-U plasma parameters. Spectroscopic measurements show that GDC reduces impurities and increases the electron temperature, enabling full-duration beam-sustained plasma operation without a large number of repeated plasma pulses. Gettering further reduces the impurities and the neutral pressure; this improved condition persists for several shots after gettering is stopped. Measurements from residual gas analyzers and an end-loss ion spectrometer show that hydrogen is present in the plasma during the initial deuterium operation after pumpdown; the hydrogen level decreases after plasma operation with gettering, indicating reduced wall recycling.
Neutral beam injection induced gas influx and desorption in the Doublet III vessel
Authors: Kim Jinchoon , Colleraine A. P. , Stewart L. D.
Published: July 2002

A method is presented of determining the gas flow from a beamline to a tokamak vessel and the gas desorption due to neutral beams impinging upon the torus wall. Time-dependent gas pressure measured both in the beamline and in the torus are matched by the corresponding theoretical solutions to arrive at unique values of the conductance between the two volumes, the desorption rate, and the pumping speed. This technique has been successfully demonstrated on the Doublet III tokamak and its beamlines.
Effect of deposition variables on the chemical vapor deposition of TiC using propane
Authors: Kim D. G. , Yoo J. S. , Chun J. S.
Published: July 2002

TiC was deposited onto cemented tungsten carbide by a chemical vapor deposition from a TiCl4–H2–C3H8 gas mixture in a horizontal resistance furnace. The deposition rate and the surface morphology of the coatings were investigated with mC/Ti, deposition temperature and total deposition pressure. Deposition rate is maximum at the mC/Ti value of about 0.9 and deposition of TiC is possible in the temperature range 850–950 °C at atmospheric pressure. By reducing the total pressure, the possible temperature range for the reaction is enlarged. The theoretical deposition efficiency and the supersaturation of reactants can also be enhanced by reducing the total pressure, which results in fine and uniform crystal size distributions. The preferred orientation of the TiC deposits is (200).
Characterization of nitrogen-containing glasses by x-ray photoelectron spectroscopy
Authors: Clabes J. G. , Fern R. E. , Frischat G. H.
Published: July 2002

Nitrogen incorporated into the matrix of oxide glasses substantially changes the physical properties of the glasses even with very low N content (1–3 wt. %). These novel oxynitride materials are known to show improved electrical resistance, dielectric constant, and mechanical properties in comparison to N-free glasses. This behavior has been attributed to the substitution of bridging O by trivalent N, causing a higher degree of linkage in the matrix. We employed XPS to address the question of the chemical environment and coordination of N in Na2O ⋅ CaO ⋅ SiO2 and Na2O ⋅ B2O3 glasses. A splitting of the N(1s) core level by ∼1.5 eV, observed for both groups of materials, demonstrates the existence of two different structural states. The core levels of N(1s) found in the N-containing glasses differ from the positions of N(1s) in reference materials such as Si3N4, BN, SiXOYNZ, and B2O3 ⋅ N suggesting a modified configuration.
Surface composition of polycrystalline Pd15Rh following high temperature oxidation in air
Authors: Graham G. W. , Potter T. , Baird R. J. , Gandhi H. S. , Shelef M.
Published: July 2002

The composition of the near-surface region of Pd15Rh polycrystalline foil heated in air was investigated by sputter depth profiling using Auger electron spectroscopy. Profiles obtained from a series of samples heated for various times (0.25–8 h) at fixed temperature in the range of 875–1125 K confirm results of a previous investigation which found that a Rh-free oxide forms on the surface below approximately 1000 K. Secondary effects of ion sputtering were identified, and in particular, the preferential sputtering of palladium with respect to rhodium was correlated with oxygen concentration. The rate at which the Rh-free oxide layer forms on the surface was observed to increase with temperature up to 1000 K. The transition from a Rh-free to a Rh-enriched oxide layer at temperatures above 1000 K appears to involve the transport of Rh toward the surface in addition to the decomposition of palladium oxide. Depth-profile data are shown to provide useful input to further detailed study of the oxide by means of optical spectroscopy.
A combination channeling study of Si(100)(2×1) reconstructed surface
Authors: Jin H.-S. , Ito T. , Gibson W. M.
Published: July 2002

Si(100)(2×1) reconstructed surface was studied by a combination of conventional (backscattering) and transmission channeling. In a conventional channeling study, the angular dependence of the conventional surface peak intensity along the normal axis 〈100〉 and off-normal axis 〈111〉 were measured and compared to several models by use of Monte Carlo simulation including the domain effect. The buckled dimer model (YC) gives better fit to the experimental results, but still underestimates the distortion in the atomic arrangement beneath the first monolayer, especially the larger displacement along the 〈100〉 axis should be considered. The measured transmission surface peak intensity is compared to the model prediction based on the flux peaking effect, indicating that, at least one of the two atoms consisting of the dimer needs to be displaced from the 〈100〉 axis larger than 0.96 Å; the displacement perpendicular to the (110) plane (Δy) should be involved. The YJM model involving the displacement Δy gives the best agreement to the measured result.
Statistical treatment of anomalous energy spread in a charged particle beam
Authors: Furukawa Y.
Published: July 2002

Increases of velocity variance and energy spread in a charged particle beam, known as the ‘‘Boersch effect,’’ were treated statistically, based on energy conservation including kinetic energy and Coulomb potential energy between charged particles. The velocity variance in a drift space was represented by the total kinetic energy, total Coulomb potential energy between particles, and total momentum of particles. The velocity variance changes according to the change of total Coulomb potential energy between particles. The generation of anomalous energy spread is due to the conversion of the Coulomb potential energy into kinetic energy. The formulas for the ultimate increase of the velocity variance and the energy spread in a drift space were derived, and a Monte Carlo simulation was performed for their evaluation. The increase of position variance by Coulomb repulsion force was also formulated. The upper limit of the anomalous energy spread of an electron beam in a drift space was calculated for various acceleration voltages and beam currents.
Reactively sputter-deposited and coevaporated TeOx thin films for optical recording
Authors: Lee W-Y. , Sequeda F. , Salem J. , Lim G. , Davis C. R. , Coufal H.
Published: July 2002

The preparation of TeOx-based optical recording media by coevaporating TeO2 and Te and by reactive sputtering of Te is reported. The composition of the reactively sputter-deposited TeOx film is found to depend linearly on the O2 partial pressure used. Like the coevaporated films, these films are amorphous as deposited and are a mixture of Te and TeO2. Both oven and pulsed-laser annealing tend to induce substantial optical property changes in these films. The temperature at which this optical property change occurs during oven annealing was found to increase with increasing x value of the film. For the laser-annealed films, the optical reflectivity was found to increase slowly even after laser irradiation, not reaching a plateau value until several minutes later. The optical property changes are attributed to the amorphous-to-crystalline phase transformation and to the segregation of Te from the TeO2 matrix and the gradual growth of these segregated Te crystallites after annealing. The effects of the number of nuclei and defects in the films on the Te crystal growth after laser annealing are also reported.
Ion assisted selective thin film deposition
Authors: Berg S. , Nender C. , Gelin B. , Östling M.
Published: July 2002

Ion bombardment of a growing film is one known way of changing film properties. Also in reactive etching, ions may assist surface reactions. We will present a study where different substrates are bombarded by energetic argon ions during deposition of titanium. If titanium is deposited onto three different substrates without influencing the substrate by any ion irradiation, a thin titanium film, equally thick, will be formed on all three substrates. If, however, the substrates are bombarded by energetic argon ions (500–800 eV) during deposition of titanium, we have found that quite different film thicknesses may be obtained on different substrates. In fact, a balance may be found where actually one substrate is sputter etched while another substrate under identical deposition conditions (same run) is deposited by titanium. Results from rf-bias sputtering in argon shows selectivity, e.g., between Si and Pt at 10 mTorr pressure, 1600 V target voltage and 800 V substrate bais. Ti is deposited onto silicon but the net surface effect on Pt is substrate etching. This demonstrates that selective deposition is possible to achieve by ion assisted thin film growth.
Temperature dependence of pumping speed for H2 of a cryosorption pump with a condensed gas layer sorbent
Authors: Arakawa I. , Tuzi Y.
Published: July 2002

Pumping speed Sm of a cryosorption pump for H2 was measured and the effect of surface temperature Ts (6–11 K) was examined at the working pressure range from 10−7 to 10−5 Pa. The sorbent was a porous layer of condensed CO2. Abnormal temperature dependence (dSm/dTs>0) was found when both the amount adsorbed C and the flow rate QH of H2 were relatively low (C<0.05 and Q<3×10−6 Pa m3/s). The author believes that this is due to the diffusion of H2 in the condensed CO2 layer, which is the rate determining process for pumping under such conditions.