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Graphene films grown by chemical vapour deposition have unusual physical and chemical properties that offer promise for applications such as flexible electronics and high-frequency transistors.sup.1-10. However, wrinkles invariably form during growth because of the strong coupling to the substrate, and these limit the large-scale homogeneity of the film.sup.1-4,11,12. Here we develop a proton-assisted method of chemical vapour deposition to grow ultra-flat graphene films that are wrinkle-free. Our method of proton penetration.sup.13-17 and recombination to form hydrogen can also reduce the wrinkles formed during traditional chemical vapour deposition of graphene. Some of the wrinkles disappear entirely, owing to the decoupling of van der Waals interactions and possibly an increase in distance from the growth surface. The electronic band structure of the as-grown graphene films shows a V-shaped Dirac cone and a linear dispersion relation within the atomic plane or across an atomic step, confirming the decoupling from the substrate. The ultra-flat nature of the graphene films ensures that their surfaces are easy to clean after a wet transfer process. A robust quantum Hall effect appears even at room temperature in a device with a linewidth of 100 micrometres. Graphene films grown by proton-assisted chemical vapour deposition should largely retain their intrinsic performance, and our method should be easily generalizable to other nanomaterials for strain and doping engineering. A growth process in which protons decouple graphene from the underlying substrate greatly reduces the number of wrinkles that usually degrade large graphene films grown by chemical vapour deposition., Author(s): Guowen Yuan [sup.1] [sup.2] , Dongjing Lin [sup.1] [sup.2] , Yong Wang [sup.1] [sup.2] , Xianlei Huang [sup.1] [sup.2] , Wang Chen [sup.1] [sup.2] , Xuedong Xie [sup.1] [sup.2] [...]

Abstract: This study was designed to determine if surface modification via photo-initiated chemical vapor deposition (PICVD) affects the physicochemical properties of polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA) differently, given [...]

Diamonds, one of the hardest materials on Earth, are so strong that they can protect fragile quantum states that would otherwise survive only in a vacuum or at ultra-cold temperatures. Engineers are mastering the art of growing diamonds with special properties and detecting their quantum spins -- opening up a range of sensing applications in the life sciences and elsewhere. Diamonds, one of the hardest materials on Earth, are so strong that they can protect fragile quantum states that would otherwise survive only in a vacuum or at ultra-cold temperatures. Engineers are mastering the art of growing diamonds with special properties and detecting their quantum spins -- opening up a range of sensing applications in the life sciences and elsewhere., Author(s): Neil Savage Author Affiliations: How quantum diamonds work: from imaging magnetic fields to detecting viruses Download a PDF of the graphic Growing diamonds Engineers can synthesize diamonds in several [...]

Film properties of hydrogenated amorphous silicon (a-Si:H) fabricated by 'liquid-Si printing' (LSP) were investigated in detail and compared to the conventional plasma enhanced chemical deposition (plasma-CVD) method. LSP a-Si:H films (LSP films) had lower film density and larger size void than the a-Si:H films deposited by plasma-CVD (CVD films). On the other hand, the LSP films had high photoconductivity comparable to device grade a-Si:H films and higher photostability than the CVD films. Thus, the LSP films were drastically different from conventional CVD films. The conversion efficiency of the bifacial solar cells (glass/TCO/n(LSP film)/i(LSP film)/p(CVD film)/TCO/electrode), which was a problem because of the missing link between high photoconductivity and low cell performance, were improved. Undoped CVD film was inserted between the i- and p-layers to suppress the plasma damage to the active layer printed by LSP when depositing a B doped a-Si:H by plasma-CVD. As a result, we achieved conversion efficiencies of 1.1% with n side incidence and 3.1% with p side incidence. PACS Nos.: 78.56.-a, 61.43.Dq. Nous etudions en detail des films de a-Si:H fabriques a l'aide d'une imprimante au Si liquide (LSP) et les comparons a ceux obtenus par la methode conventionnelle de depot chimique en phase vapeur avec traitement au plasma (plasmaCVD). Les films a-Si:H fabriques a l'aide d'une imprimante (LSP) ont une densite de film plus faible et des lacunes plus grosses que des films deposes par plasma-CVD. D'un autre cote, les films LSP ont une haute photoconductivite comparable a des films a-Si:H de haute qualite et une plus grande photo-stabilite que des films CVD. Les films LSP sont notablement differents des films CVD conventionnels. Nous ameliorons le rendement de conversion de cellules solaires bifaciales (verre/TCO/n(film LSP)/i(film LSP)/p(film CVD)/TCO/electrode) qui etait un probleme a parce qu'il n'y avait pas de lien entre haute conductivite et basse performance de la cellule. Nous inserons un film CVD non dope entre la couche i et la couche p pour eliminer le dommage plasma a la couche active imprimee par LSP, lorsqu'on depose un a-Si:H dope au B par plasma-CVD. Le resultat est que nous realisons un rendement de conversion de 1.1 % pour une incidence cote n et de 3.1 % pour une incidence cote p. [Traduit par la Redaction], 1. Introduction Thin-film silicon solar cells are a candidate for high cost-performance solar cells. We successfully obtained the deposition criteria for high quality amorphous Si (a-Si:H) films deposited by plasma [...]

Monolayer graphene was first obtained (1) as a transferable material in 2004 and has stimulated intense activity among physicists, chemists and material scientists (1-4). Much research has been focused on developing routes for obtaining large sheets of monolayer or bilayer graphene. This has been recently achieved by chemical vapour deposition (CVD) of C[H.sub.4] or [C.sub.2][H.sub.2] gases on copper or nickel substrates (5-7). But CVD is limited to the use of gaseous raw materials, making it difficult to apply the technology to a wider variety of potential feedstocks. Here we demonstrate that large area, high-quality graphene with controllable thickness can be grown from different solid carbon sources--such as polymer films or small molecules--deposited on a metal catalyst substrate at temperatures as low as 800 °C. Both pristine graphene and doped graphene were grown with this one-step process using the same experimental set-up., With its extraordinary electronic and mechanical properties, graphene is showing promise in a plethora of applications (7-13). Graphene can now be obtained by several different approaches. The original mechanical peeling [...]

The synthesis of the gas chromatography stationary phase by molecular self-assembly of carbon nanotubes (CNTs) via a novel ethanol chemical vapor deposition process is presented. A major advantage is that ethanol was found to be an excellent carbon source that generated highly pure multiwalled carbon nanotubes with very little nontubular carbon impurities. The nanotubes were not vertically aligned but lay fiat out on the column surface in a randomly distributed configuration. The CNT phase was able to separate a wide range of organic compounds with diverse polarity and volatility, where the number of plates per meter ranged from 900 to 1280. It also showed classical chromatographic behavior and good precision. 10.1021/ac100428m

A dielectric barrier discharge is generated by flowing helium and hydrogen through a microreactor capillary which contains a coating of Ni/alumina catalyst to activate carbon nanofiber (CNF) synthesis. Optical and electrical measurements have been done to characterize the discharge during catalyst treatment. A sinusoidal voltage of 6 kV (peak) with a frequency of 50 kHz has been applied to a high-voltage electrode, and a helium gas flow stabilizes the discharge to have a uniform and high-power-density surface treatment. Cold-plasma operation for 15 min is simple and audiovisual, increases the CNF yield significantly compared to nonactivated samples, and can compete with high-temperature treatment at 973 K for 2 h. Increasing the discharge treatment duration to 30 min results in sintering of catalyst particles and nonuniform growth of the nanofibers. Index Terms--Barrier discharge, carbon nanofiber (CNF), catalyst, chemical vapor deposition (CVD), microplasma, microreactor.

Plasma polymerization at atmospheric pressure is used to obtain stable hydrophobic coatings onto various substrates. Plasma is generated in a dielectric barrier discharge configuration using a mixture of helium gas and styrene vapors. The discharge is characterized by means of electrical measurements and optical emission spectroscopy. Since the styrene vapors introduced in plasma provide a significant decrease of the discharge current, we established the optimum parameters (voltage waveform, gap length, and gas flow rates) for plasma polymerization, assuring a maximum discharge current. The plasma-polymerized films (polystyrene), deposited onto the glass or silicon substrates, are analyzed by contact angle measurements, ellipsometry, IR spectroscopy, and atomic force microscopy (AFM). The film thickness is measured by light interferometry and confirmed by AFM analysis. The water contact angles are higher than 130[degrees], proving the hydrophobic characteristics of the film, and the refractive index is around 1.5, corresponding to the values of commercial polystyrene. Index Terms--Coatings, materials science and technology, plasma applications, plasma chemical vapor deposition, plasma diagnostics, polymers.

In this paper, homogeneous and dense silicon-based coatings have been deposited from hexamethyldisiloxane (HMDSO: [Si.sub.2]O[(C[H.sub.3]).sub.6]) on patterned silicium in a Townsend dielectric barrier discharge operating at atmospheric pressure. A brief description of the physical mechanisms ruling the step coverage is first described, followed by a description of the atmospheric pressure plasma process used. The step coverage is discussed with regard to the aspect ratio of the patterned wafers. Coatings deposited in and after the discharge region have also been characterized to understand the influence of plasma activation. In order to understand the experimental results, numerical simulations have been performed using a simplified reactive transport model. These results provide information and first general insight on the physical mechanisms ruling the conformity of silicon-based films deposited with this technique. Index Terms--Atmospheric pressure Townsend discharge (APTD), dielectric barrier discharge (DBD), glow discharges, plasma-enhanced chemical vapor deposition (PECVD), reactive transport modeling, silicon oxide, step coverage.

In this paper, the deposition and characterization of plasma-polymerized polystyrene (pp-PS) using PECVD under atmospheric pressure on a variety of substrates was investigated. An atmospheric RF plasma torch and an HF dielectric-barrier-discharge (DBD) system were used to deposit thin pp-PS coatings on PTFE, HDPE, stainless steel, glass, and silicon wafer. The styrene vapor was carried by Ar or He. The pp-PS films were characterized by Fourier transform infrared spectroscopy (FTIR) (infrared reflection absorption spectroscopy), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA), static secondary ion mass spectroscopy (SSIMS), and optical microscopy, and the plasma phase was studied by optical-emission spectroscopy. The major features that characterize PS are present in the FTIR, SSIMS, and XPS spectra of our films, although some differences are observed between pp-PS and their conventionally polymerized counterparts: oxygenation, branching, degree of cross-linking, and unsaturation. According to the WCA and XPS results, the films deposited by the RF plasma torch (placed in a Plexiglass chamber) are more oxygenated than those deposited by DBD, which is operated under a much more controlled atmosphere. A comparison of the chemical structure of the deposited coatings (branching, cross-linking) as a function of the nature of the carrier gas was established by FTIR: pp-PS synthesized in the presence of Ar (for both processes) exhibit more branching and a higher degree of cross-linking than pp-PS synthesized with He as the main plasma gas. The optical microscopy points out a diversity of structures that depend on the nature of the substrate and the plasma parameters. Index Terms--Plasma CVD, plasma materials-processing applications, plasmas, plastics.

A large-scale atmospheric pressure plasma has been generated in helium, and the time-resolved optical and electrical properties have been shown to produce a homogeneous dielectric barrier discharge. Introducing tetraethyl orthosilicate as a liquid aerosol into this plasma produced clear, uniform, and smooth plasma polymerized coatings. Optical imaging studies have shown that adding 1% oxygen to the gas mixture induced a switch from a homogeneous plasma to a filamentary or microdischarge mode of operation, and this has been shown to dramatically alter the morphology of the deposited coatings. Surface analysis reveals significant particulate inclusions in coatings deposited from the filamentary mode of operation. Index Terms--CVD, optical imaging, plasma properties, thin films.

Pulsed dielectric-barrier discharge was used to modify polycarbonate surfaces by applying a thin film of silicone oxide. The discharge was supplied by alternating voltage pulses that lasted for about 50 ns. The generated current pulses were shorter and lasted for about 20 ns. For this reason, high power is concentrated in short time. Analysis of the composition thin film by means of the X-ray photoelectron spectroscopy method shows that it consists mainly of silicon, oxygen, and carbon. Based on the concentrations of these elements, films can be divided into three parts. In this paper, the influences of parameters characterizing the plasma reactor are attributed to a charge transferred in the single pulse of discharge, a power of discharge, and a microstructure of discharge. The influences of these parameters on deposition rate are shown. Index Terms--Dielectric breakdown, plasma CVD, thin films.

We have demonstrated resonant frequency tuning of nanowire resonator operated in both atmospheric circumstance and high vacuum environment using electrostatic spring-softening effect. The nanowire is synthesized at any desired position by focused ion beam-chemical vapor deposition (FIB-CVD) on the sidewall of batch-processed micro electrode. The resonant frequency in a vacuum chamber of 2.5 x [10.sup.-4] Pa is 1.564 MHz under the driving voltage of 5 [V.sub.DC] [+ or -] 5 [V.sub.AC]. When 30 [V.sub.DC] tuning bias is applied on tuning electrode, the resonant frequency is reduced to 1.529 MHz due to the electrostatic spring-softening effect while the driving bias is maintained. For the tuning bias of 60 V, the resonant frequency at atmospheric pressure has been tuned from 1.49 MHz to 1.41 MHz under the c riving voltage of 30 [V.sub.DC] [+ or -] 10 [V.sub.AC]. The method demonstrated both in high vacuum and at atmospheric pressure is a simple and effective way to tune the deviated resonant frequency of nanowire resonator to the desired value without the alteration of the structure or post fabrication process. Index Terms--Electrostatic force, electrostatic spring effect, focused ion beam-chemical vapor deposition (FIB-CVD), frequency tuning, nanowire resonator, resonant frequency.

Polycrystalline artificial diamond produced by chemical vapor deposition (pCVD) is a possible sensor material for the beam calorimeter of the ILC. The requirements are linearity over a large range of flux and radiation hardness against a total ionizing dose of several MGy per year of operation. A hadron test beam at the CERN PS was used to study the linearity of the response of pCVD sensors. An electron test beam at the S-DALINAC was used to measure the charge collection distance (CCD) as a function of the absorbed dose up to several MGy. Current-voltage characteristics of these sensors were measured before and after the irradiation as well as the dependence of the CCD on the applied electric field before and after the irradiation. Index Terms--BeamCal, charge collection distance, CVD diamond sensor, FCAL, forward calorimetry, ILC, irradiation, pumping, radiation hardness.

This paper presents the fabrication and demonstration of an ultrathin microelectromechanical chemical sensing device. Microcantilevers are etched from 100-nm-thick silicon nitride, and a 75-nm-thick reactive copolymer film for sensing is deposited by initiated chemical vapor deposition. Cross-linking densities of the polymer films are controlled during the deposition process; it is shown that greater cross-linking densities yield greater cantilever deflections upon the polymer's reaction with the analyte. Considering that chemical reactions are necessary for stress formation, the sensing is selective. Cantilever deflections of greater than 3 [micro]m are easily attained, which allow a simple switch to be designed with resistance-based outputs. When exposed to a hexylamine vapor-phase concentration of 0.87 mol%, the resistance of the switch drops by over six orders of magnitude with a response time of less than 90 s. [2008-0132] Index Terms--Chemical-vapor deposition (CVD), microsensors, thin films, three-dimensional nanomanufacturing.

We demonstrate a novel photoplastic nanoelectro-mechanical device that includes an encapsulated polysilicon piezoresistor. The temperature limitation that typically prevents deposition of polysilicon films on polymers was overcome by employing a hotwire CVD process. In this paper, we report the use of this process to fabricate and characterize a novel polymeric cantilever with an embedded piezoresistor. This device exploits the low Young's modulus of organic polymers and the high gauge factor of polysilicon. The fabricated device fits into the cantilever holder of an atomic force microscope (AFM) and can be used in conjunction with the AFM's liquid cell for detecting the adsorption of biochemicals. It enables differential measurement while preventing biochemicals from interfering with measurements using the piezoresistor. The mechanical and electromechanical characterization of the device is also reported in this paper. [2008-0108] Index Terms--Affinity cantilevers, bio-microeleetromechanical system (bio-MEMS), hotwire CVD (HWCVD), piezoresistive sensing, polymeric cantilevers, surface stress.

This paper covers the design, fabrication, and characterization of two-layer microcoils wherein an unannealed plasma-enhanced CVD Si[O.sub.2] functions as the insulator between silicon-and photoresist-molded copper coils. This design overcomes the thermal limitations placed upon coils that are embedded within polymer molds and thereby enables higher current carrying capability. The fabrication process is compatible with deep reactive-ion etching and may be used to integrate coils with flexures/compliant mechanisms. Thermal and mechanical limitations were determined experimentally and used to create design rules that limit the coil design space. The breakdown strength of the unannealed Si[O.sub.2] was measured at 4.6 MV/cm. Experiments show that coils with 40-[micro]m pitch, 30 x 30-[micro][m.sup.2] winding cross section, and Si[O.sub.2] thickness of 1 [micro]m may carry more than 1 A (larger than [10.sup.9] A/[m.sup.2]) with less than 10[degrees]C temperature change. These characteristics make the coils useful in small-scale actuators and power systems. [2008-0170] Index Terms--Copper damascene, electroplating, magnetic microactuator, microcoil, microelectromechanical devices, silicon dioxide.

Single crystal diamond produced by chemical vapor deposition (CVD) at very high growth rates (up to 150 [micro]m/h) has been successfully annealed without graphitization at temperatures up to 2200[degrees]C and pressures microwave plasma | hydrogen | vacancy | nitrogen

A straightforward procedure is described for preparation of arrays of microdisk electrodes comprising bundles of vertically aligned carbon nanotubes (VACNTs). The arrays are fabricated by thermal chemical vapor deposition synthesis directly on a planar carbon film support. Use of standard micro-and nanolithography procedures for patterning the bilayer catalyst spots enables arrays to be grown with controlled electrode diameters and spacings. The minimum accessible VACNT bundle diameter, and hence microelectrode diameter, is 2 [micro]m. After insulating the arrays with SU-8 epoxy and exposing the VACNT ends by polishing or treating with [O.sub.2] plasma, the microdisk electrodes exhibit attractive electrochemical properties.

An analytical model that simulates the current gain improvement of polysilicon-emitter bipolar transistors based on the effective recombination velocity method is presented. The dependence of the current gain on the physical parameters indicated that the transport mechanism governing the gain improvement depended on the chemical interface treatment performed prior to polysilicon deposition and the anneal temperature.

The characteristics and operation of an InAs enhancement-mode field-effect transistors integrated directly on Si substrates is reported. The temperature-dependent measurements revealed activation energy of about 200 meV for the InAs/Si conduction band offset.

Plasma chemical technology is experimentally applied to the fabrication of a Bi-activated alumosilicate-core pure-silica-cladding fiber preform. To the best of our knowledge, this is the first time this technology has been applied in this way. We measure gain efficiency at pumping by a 1058 nm wavelength Yb fiber laser in a piece of a newly obtained fiber 20 m in length within 100-1200 nm wavelengths band. The gain efficiency reaches as high as 0.2 dB/mW. Bi-activated alumosilicate-core pure-silica-cladding fiber that is not more than 12 m in length serves a basis for a 1 W output power fiber laser emitting at the wavelength of 1160 nm with 8% slope efficiency. We also measure the photoluminescence spectrum and kinetics of Bi centers responsible for laser emission under the excitation of 193 nm wavelength ArF laser pulses. OCIS codes: 060.2290, 060.2320, 140.3510, 140.3380, 140.4480.

Si[O.sub.2]/[Si.sub.3][N.sub.4] double layers electrets have been investigated for their long-term charge stability and compatibility to micro technology. This paper first reports Si[O.sub.2]/[Si.sub.3][N.sub.4] double layers electrets both prepared by plasma enhanced chemical vapor deposition (PECVD) on glass substrates. Charging time, charging temperature and annealing process were studied for their influence on electrets properties. Different methods of treatment, such as hexamethyldisilazane (HMDS) coating, heat treatment at 250 [degrees]C, [O.sub.2] plasma treatment and their combinations, were employed to improve charge stability under high humidity conditions. The experimental results show that PECVD prepared Si[O.sub.2]/[Si.sub.3][N.sub.4] double layers exhibit high performance in charge storage under different environmental conditions. The surface potential did not decay obviously at room temperatures during more than two months. The samples lose less than 20% of the surface potential at 250 [degrees]C for more than 10 h. The surface potential could be kept more than 90% at 95% RH by heat treatment combined with HMDS process or [O.sub.2] plasma treatment. Index Terms--Double layers, electrets, PECVD, Si[O.sub.2]/[Si.sub.3][N.sub.4].

This research is directed at the development of Electrostatic Actuated NAno Tensile testing devices (EANATs) for measuring mechanical properties of carbon nanowires, deposited by focused ion beam-assisted chemical vapor deposition (FIB-CVD) using phenanthrene gas. The EANATs were composed of the specimen part, actuator part and measurement part. 1000, 3000 and 5000 pairs of comb drive actuators were prepared within the actuator part for stretching the nanowires. The measurement part had a cantilever used as a lever motion amplification system for measuring tensile displacement of the nanowires. A theoretical resolution of 0.17 nm in tensile displacement was achieved using the amplification system and imaging analysis. The uniaxial tensile force was derived from the total spring constant of suspended beams built within the EANATs, with the theoretical resolutions ranging from 108 to 113 nN. This research was therefore successful in obtaining accurate load-displacement curves for carbon nanowires. The Young's modulus observed for the nanowires provided the scatter in absolute values ranging from 42.6 to 80.7 GPa. The fracture stress and strain of the nanowires exhibited larger values of 4.3 GPa and 0.08 strain, respectively. Discussion of the deformation behaviors and failure mechanisms of the nanowires is made from FE-SEM observations of the nanowires before and after tensile failure. [2006-0033] Index Terms--Carbon nanowire, electrostatic comb-drive actuator, focused ion beam-assisted chemical vapor deposition (FIB-CVD), fracture stress and deformation behavior, tensile test, Young's modulus.

Various researches are conducted to study and explain the effects of the filling gas on the deposition of amorphous diamondlike carbon films by the technique of dense plasma focus system at the room temperature. The results obtained from the scanning electron microscopy and X-ray diffraction spectra show that the film deposition rates at the room temperature is quite high with the deposition of amorphous carbon a-C films without a crystalline peak.

An analysis of a fluid model is used to simply describe the phenomenon of microwave plasma discharge for the chemical vapor deposition of diamond with extremely reduced computational cost. The model gives a full description of the electron temperature, as well as the number density of the substance.

A study was conducted to investigate the origins of the very low hydrogen concentrations observed in the a-Si:H films prepared by using a triode deposition system. The finding reveal that due to a steric hindrance, the hydrogen elimination process during film growth is disturbed when higher silane radicals stick to a growth surface which contributes to short diffusion length and frequent collisions with silane molecules.

The morphology of basal plane dislocations (BPDs) in 4H-SiC homoepitaxial layers was investigated using plane-view transmission x-ray topography and molten KOH etching. Based on the morphologies three types of BPDs are distinguished which include interfacial dislocations, curved dislocations and circular loop dislocations around micropipes.

Various gas mixtures are employed to deposit several microcrystalline, nanocrystalline and ultrananocrystalline diamond films with the help of hot filament chemical vapor deposition for all the possible experimental conditions. The analysis reveals that the use of a model based on competition between various radical species and dangling bonds on the surface can easily rationalize the observed film morphology, growth rate, nucleation and crystal size of the diamonds.

The laser-assisted chemical vapor decomposition of ferrocene vapor in Ar gas atmosphere is used to form iron nanoparticles enclosed in carbon shells, thus the particle size dependence on the total ambient gas pressure and on laser fluence of the pulsed ArF excimer laser is investigated. The observations demonstrate that alpha-Fe and gamma-Fe phases existed for the single crystalline iron cores, surrounded by graphitic and amorphous carbon layers.

Laser-assisted chemical vapor deposition (CVD) is used to fabricate three-dimensional (3D) spherical-shell photonic band gap (PBG) structures by depositing silicon shells covering silica particles. The spherical silicon-shell array structures can be optimized by changing precursor pressure and laser parameters and higher amplification ratio of silicon can yield a large complete PBG.

The deposition of in situ boron-doped polycrystalline silicon-germanium (poly-SiGe) films in a conventional low-pressure chemical-vapor deposition reactor has been characterized using the design of experiments method. The dependencies of deposition rate, resistivity, average residual stress, strain gradient, and wet etch rate in hydrogen peroxide solution are presented. Structural layer requirements for general microelectromechanical system applications can be met within the process temperature constraint imposed by complementary metal-oxide-semiconductor (CMOS) electronics. However, residual stress and strain gradient requirements for inertial sensor applications will be difficult to meet with a single homogeneous layer of poly-SiGe that is about 2 [micro]m thick. By correlating stress depth profile measurements with cross-sectional transmission electron microscopy images, we conclude that the large strain gradient is due to highly compressive stress in the lower (initially deposited) region of the film. For films deposited at very low temperature (near the range of amorphous film deposition), in situ boron doping enhances film crystallinity and reduces the strain gradient. Index Terms--Design of experiments, low-pressure chemical-vapor deposition (LPCVD), microelectromechanical systems (MEMS), microstructure, poly-SiGe, process integration, strain gradient.

The direct Monte Carlo method (DMCM) is used to study enhancements in rates of ionization, dissociation and current in the dc saddle field (DCSF) glow discharge. It is observed that the DCSF operates at low pressures with efficiency, which makes it attractive for the production of thin films whose qualities are sensitive to gas phase reactions.

The lasing characteristics of three- and five-stack InAs/GaAs quantum dot (QD) lasers are reported which are grown by metal organic chemical vapor deposition. It is found that lasing can be achieved from the ground state at 1135 nm for device lengths as short as 1.5 mm, by increasing the number of stacked dot layers.

Various studies are conducted to study the surface morphologies of BiSb[Te.sub.3] films grown on (001) GaAs vicinal surfaces, which helps in understanding the phenomenon behind their growth by metal organic vapor phase epitaxy. The results show that a regular array of terrace step structures of the films can be observed on the surfaces, which is only due to the preferential incorporation of adatoms at step sites and lateral growth anisotropy.

The effect of oxidation on the chemical bonding structures of silicon nitride thin films synthesized by a low-temperature plasma-enhanced chemical vapor deposition (PECVD) method is investigated. The crystalline silicon dioxide is found to be stoichiometric Si[O.sub.2], whereas the remaining matrix is found to be a nonstoichiometric silicon oxynitride conforming to the random bonding model.

Photoluminescence (PL) from purified (>90%) double-wall carbon nanotubes (DWNTs), which are synthesized by zeolite catalyst-supported chemical vapor deposition (zeolite-CCVD) of very small diameters (0.8-nm average inner tube) is presented. The PL contour mappings of various ratios (1-90%) of double-versus single-wall carbon nanotubes by thermal oxidation enabled to unambiguously identify the chirality of inner tubes for the DWNTs synthesized.

Results on the nanostructure and nanochemistry of epitaxial Cu([In.sub.1-x][Ga.sub.x])[Se.sub.2] (CIGS) grown by metal organic vapor phase epitaxy on GaAs (001) substrates are described. The growth process results in two-phase film with [Cu.sub.2]Se segregated on the surface suggesting that the CIGS growth is properly a solid-phase reaction between [Cu.sub.2]Se and group III elements in the CIGS or dissolved in the [Cu.sub.2]Se from the vapor phase.

A study concerning the tautness of suspended carbon nanotubes (CNTs) grown using the chemical vapor deposition (CVD) method is presented. The high-resolution scanning electron microscope (HR-SEM) and transmission electron microscope (TEM) investigations revealed that the interaction between CNTs among themselves as well as with the surface on which they are grown is a primary cause for the tautness of suspended tubes.

The densities of N, NH, N[H.sub.2] radicals in a remote Ar-N[H.sub.3]-Si[H.sub.4] plasma used for high-rate silicon nitride deposition are examined for different gas mixtures and plasma settings by using cavity ringdown absorption spectroscopy and threshold ionization mass spectroscopy. It is concluded that N and N[H.sub.2] radicals are mainly responsible for the N incorporation in the silicon nitride film, while Si atoms are most likely brought to the surface in the form of Si[H.sub.x] radicals.

Density functional theory (DFT) calculations and statistical thermodynamics were used to evaluate metal-organic chemical vapor deposition (MOCVD) growth of tungsten nitride (W[N.sub.x] and tungsten carbonitride (W[N.sub.x][C.sub.y]) thin films from the complexes [Cl.sub.4](C[H.sub.3]CN)W(NR). Results are consistent with facile dissociation of the acetonitrile ligand (C[H.sub.3]CN) in the temperature range used for CVD.

Relaxor-type ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) films, 2-3 mum in thickness, with a PbTiO3 content (x) ranging from 0 to 1 were grown on [(100).sub.c]SrRuO3 ll (100)SrTiO3 substrates at 650 degree Celsius by metal-organic chemical vapor deposition. The constituent phase changed from a rhombohedral (pseudocubic) single phase, a mixture phase of rhombohedral (pseudocubic) and tetragonal phases, and a tetragonal single phase, with increasing x.

The variable stripe length (VSL) method is used to investigate the optical gain in GaN epilayers. Gain peak values up to ~7500 [cm.sup.-1] is shown in GaN epilayers grown on AIN buffer layers deposited on sapphire by migration enhanced metal-organic chemical vapor deposition.

The kinetics of roughening and smoothing in Ge(001) surface morphology during synchrotron-radiation-excited Ge[H.sub.4]-source homoepitaxy are examined. Roughening is terminated when all dangling bonds are tied up with H atoms and in smoothing process, valleys are preferentially embedded and a two-dimensional (2D) flat film is eventually recovered with no defects in the Ge film.

Growth of (vertically aligned small-diameter multiwalled carbon nanotubes) VA-MWNT films and microstructures from a Fe/Al(sub 2)O(sub 3) catalyst film deposited by electron beam evaporation is discussed. The flow profile over the sample mediates the supply of reactants to the catalyst and that pretreatment using H(sub 2) significantly affects the initial activity of the catalyst.

A thorough study of the growth of self-assembled GaN/AIN quantum dots (QDs) is reported. These QDs are grown on sapphire substrates using the Stranski-Krastanov (SK) growth mode by means of low-pressure metal organic vapor dphase epitaxy.

DNA immobilization enhancement is demonstrated in a structure consisting of ZnO nanotips on 128 degree Y-cut LiNbO3 and the effects of ZnO nanotip on the surface acoustic wave (SAW) responses are investigated. The ZnO nanotip enhance the DNA immobilization by a factor of 200 compared to ZnO film with flat surface.

Homoepitaxial silicon thick films are produced by medium pressure plasma chemical vapor deposition at rates as fast as 60nm/s and at a temperature of around 700 degree celsius, with a aline gas partial pressure of 4mTorr. The rate for epitaxial growth is observed to increase linearly with saline gas partial pressure.

The effect of growth temperature and gas flow ratio on alloy composition and growth rate is investigated for the chemical vapor deposition (CVD) synthesis of pseudomorphic Si(sub (1-x))Ge (sub x) alloys grown at reduced pressure in a reaction rate limited regime. A model to support the empirical laws found without making any assumption on the mechanism and it is extended to the full compositional range of CVD grown Si-Ge alloys.

Atomic-layer-deposited Al2O3 gate stacks with ST and SN are compared for studying their effects on the properties of deposited gate dielectric stacks. X-ray photoelectron spectroscopy results indicate that both surface pretreatments are beneficial for compact Al2O3 deposition, and however, the sample with SN shows much better interface thermal stability.