摘要:

The stress evolution of plasma enhanced chemical vapor depositiona‐SiC:H films was studied by increasing the annealing temperature from 300 to 850 °C. A large stress range from −1 GPa compressive to 1 GPa tensile was investigated. Infrared absorption, x‐ray photoelectron spectroscopy, and elastic recoil detection analysis techniques were used to follow the Si‐C, Si‐H, and C‐H absorption band evolutions, the Si2pand C1schemical bondings, and thea‐SiC:H film hydrogen content variations with the annealing temperatures, respectively. It is pointed out that the compressive stress relaxation is due to the hydrogenated bond (Si—H and C—H) dissociation, whereas the tensile stress is caused by additional Si—C bond formation. At high annealing temperatures, a total hydrogen content decrease is clearly observed. This total hydrogen loss is interpreted in terms of hydrogen molecule formation and outerdiffusion. The results are discussed and a quantitative model correlating the intrinsic stress variation to the Si—H, C—H, and Si—C bond density variations is proposed.

ISSN:0021-8979    

DOI:10.1063/1.354635

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Diamond nucleation on very smooth (100) silicon substrates coated with thin films of a colloidal graphite suspension was investigated with a microwave‐plasma‐enhanced chemical‐vapor‐deposition system. Nucleation densities of the order of 106cm−2were obtained by coating the substrates with carbon films of thicknesses less than 1 &mgr;m. However, very low nucleation densities were obtained with carbon film thicknesses greater than 1 &mgr;m. The effect of the carbon film thickness on diamond nucleation was examined by measuring the etching rate of carbon films exposed to a hydrogen plasma and was further interpreted on the basis of scanning electron microscopy and Raman spectroscopy results. Etching of the original carbon may lead to the formation of a thin residual carbon film when the initial film thickness is less than a critical value. Results demonstrated that the high nucleation densities of good quality cubo‐octahedral diamond crystals obtained with relatively thin carbon films were primarily due to the formation of a porous ultrathin residual carbon film. The critical initial film thickness was a function of the plasma etching and deposition rates of carbon which, in turn, affected the effective local carbon concentration. Thick carbon films yielded insignificant nucleation densities and poor quality diamond because of the high local carbon content resulting from the partial etching of carbon and the increased carbon concentration in the plasma. The local carbon concentration and the residual carbon film are the proposed principal factors for the obtained high diamond nucleation densities on unscratched silicon substrates.

ISSN:0021-8979    

DOI:10.1063/1.354636

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Optical constants of relaxed, derelaxed, and partially relaxed amorphous silicon (a‐Si) in the range 0.4–0.9 &mgr;m are reported. The thermodynamical state of amorphous silicon (a‐Si) has been changed either by thermal treatments or low dose ion implantation. Ellipsometry has been used to evaluate the complex refractive index for several amorphous states with enthalpy content between that of the fully relaxed and fully derelaxeda‐Si. We observed a strong correlation between the electronic structure as probed by our optical measurements and the topological short‐range order as probed by Raman scattering.

ISSN:0021-8979    

DOI:10.1063/1.354637

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

It is shown that plasma‐enhanced chemical‐vapor deposition (PECVD) of thin SiO2on Si wafers followed by rapid thermal annealing (RTA) can result in very high effective carrier lifetime (≳5 ms) and extremely low surface recombination velocity (≤2 cm/s). Thin SiO2(∼100 A˚) layers were prepared by direct PECVD at 250 °C and RTA was performed at 350 °C in forming gas. Detailed metal‐oxide‐semiconductor analysis and model calculations showed that such a low recombination velocity is the result of moderately high positive oxide charge (5×1011–1×1012cm−2) and relatively low midgap interface‐state density (5×1010–1×1011cm−2 eV−1). RTA was found to be superior to furnace annealing, and a forming gas ambient was better than a nitrogen ambient for achieving a very low surface recombination velocity. Some degradation in the surface recombination velocity or effective lifetime was observed. It is found that a PECVD SiN cap on top of the thin SiO2not only suppressed this degradation but also enhanced the effective lifetime.

ISSN:0021-8979    

DOI:10.1063/1.354638

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Photoluminescence has been markedly quenched and photoconductivity has been enhanced by more than one order of magnitude upon introduction of several mol% of buckminsterfullerene (C60) to poly(2,5‐dialkoxy‐p‐phenylene vinylene) (RO‐PPV), especially at excitations about 2.2 eV, corresponding to the band gap energy of RO‐PPV and also in bands at 1.8 and 3.5 eV, which correspond to optical excitation of C60molecules, suggesting that photo‐induced charge transfer occurs between RO‐PPV and C60. On the other hand, absorption spectrum and electrical conductivity of RO‐PPV have been scarcely influenced by doping of small amount of C60, suggesting that the ground state charge transfer between C60and RO‐PPV is not effective, contrary to the case of poly(3‐hexylthiophene). These results are discussed by taking relative electronic energy states of RO‐PPV and C60into consideration. The photo‐excited exciton‐polaron (Ex‐P) in RO‐PPV is interpreted to migrate along about 100 monomer units along a polymer main chain in its lifetime and dissociates when encountered with C60. These unique doping characteristics of C60in RO‐PPV are not dependent on the alkyl chain length, contrary to the case of poly(3‐alkylthiophene).

ISSN:0021-8979    

DOI:10.1063/1.354639

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The epitaxial growth of GaAs films on on‐axis (100) Si was studied at growth temperatures in the range 160–280 °C using ionized source beam epitaxy. Single‐crystal GaAs films could be grown at a temperature as low as 160 °C with the acceleration of a partially ionized As‐source beam, whereas at the same temperature only amorphous films were possible with neutral beams or with the ionized source beam with no acceleration. The use of an ionized As‐source beam even without beam acceleration greatly improved the surface flatness of the GaAs film, and suppressed the formation of antiphase domains. The acceleration of the ionized As beam further improved the surface quality of the film.

ISSN:0021-8979    

DOI:10.1063/1.354640

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The infralow‐pressure chemical vapor deposition (ILPCVD) system has been developed to reduce the partial pressure of silane (PSiH4) to the sub‐mTorr order by increasing the pumping speed, while aiming at the improvement of as‐deposited polycrystalline silicon (poly‐Si) film qualities. The films prepared by the system show better physical properties than ordinary low‐pressure chemical vapor deposition (LPCVD) films at fixed temperature (600 °C), so that the low‐temperature processed as‐deposited poly‐Si thin film transistors can be easily and significantly improved, having ON/OFF current ratios of more than 108. Physical analyses have confirmed that the films deposited at temperatures as low as 555 °C by the ILPCVD system are undoubtedly polycrystalline. The fabrication of poly‐Si TFT’s through a low‐temperature process confirms good semiconductive behavior of the films, even when deposited at 555 °C. The superiority of the ILPCVD over other LPCVD’s is explained by the deposition kinetics. The nature of LPCVD as‐deposited polysilicon film is characterized by the competition between surface reaction rate and gas‐phase mass‐transfer rate. High‐temperature or infralow‐pressure deposition is controlled by gas‐phase mass transfer of the reactant. The mass‐transfer controlled deposition is found to be preferable to obtaining good polycrystalline silicon film, namely high crystallinity, ⟨100⟩ preferred orientation, large grains, and good semiconductive properties.

ISSN:0021-8979    

DOI:10.1063/1.354641

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Ceramic coatings of zirconium nitride have been fabricated on nickel, silicon, andM2high‐speed steel by methods of reactive magnetron sputtering ion plating (RMSP) and the dynamic ion mixing (DIM). The microhardness values of ZrN film prepared by RMSP with different nitrogen partial pressure have been discussed. The scratch tests provide that the adhesion of ZrN film produced by dynamic ion mixing is better than that by reactive magnetron sputtering ion plating. Auger electron spectroscopy analysis is used to analyze the composition distribution of ZrN film prepared by DIM and indicates that there is a transitional layer between the ZrN film and substrate. Meanwhile, by cross‐sectional and the plan‐view transmission electron microscopy, it is observed that the interlayer of amorphous structure exists in the interface zone between ZrN film and substrate. According to the analysis of energy‐dispersive x‐ray analysis patterns, the composition of this amorphous region fabricated by RMSP is Ni51Zr49(≊NiZr), as is that fabricated by DIM. (Up to now it has not been reported that the amorphous transitional layer occurs in reactive magnetron sputtering ion plating). The reason why the adhesion of coating by DIM is better than that by RMSP is not the formation of the transitional layer in ion‐beam‐assisted deposition but the particle bombardment effects on the bulk of the thin film.

ISSN:0021-8979    

DOI:10.1063/1.354642

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We obtain undopedn‐type GaSb epilayers by low‐temperature metalorganic chemical vapor deposition at a low growth temperature of 450 °C reproducibly. Different conduction types of GaSb and different energy levels are compared by photoluminescence spectra. Forn‐type undoped GaSb, the FWHM of dominant peak and bound exciton are 11 and 1.3 meV, respectively. Because semi‐insulating GaSb substrates cannot be obtained, we cannot use the Hall effect to determine the carrier concentration and mobility of the homoepilayer. In order to identify the conduction types of GaSb, ohmic contact and Schottky barrier are made by Au/Ge/Ni and Au, respectively. The concentrations of undopedn‐type GaSb homoepilayers obtained fromI‐VandC‐Vmeasurements are 1.44×1017–3.0×1017cm−3, respectively. The mobility and concentration of undopedp‐type GaSb heteroepilayers are 758 cm2/V s and 9.0×1015cm−3at 300 K, respectively.

ISSN:0021-8979    

DOI:10.1063/1.354643

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Ferroelectric PbTiO3films were deposited by ion‐beam‐assisted deposition (O2+Ar 75–150 eV). The effects of ion bombardment on the Pb/Ti ratio and the structures of the film are discussed. For a given target‐substrate distance and substrate temperature, the Pb/Ti ratio decreased with increasing bombarding beam energy. Compared with the films deposited without ion bombardment, the deposition rate was increased under ion bombardment, which is attributed to an increase in the surface reaction rate. The crystal grains are larger for films deposited under ion bombardment, which implies that ion bombardment enhances the surface mobility of adatoms and hence the growth kinetics of the growing films. Dielectric and ferroelectric properties of the as‐deposited films are also reported.

ISSN:0021-8979    

DOI:10.1063/1.354644

出版商:AIP    

年代:1993

数据来源: AIP