摘要:

The selectivity of copper deposition from copper (II) bis‐hexafluoroacetylacetonate on SiO2patterned with a platinum seeding layer is studied as a function of the reagent gas mixture. On platinum, the copper film growth rate increases with the amount of water vapor in the gas flow, and is independent of the chemical nature of the carrier gas used (H2or He). The selectivity of the copper deposition is significantly improved when using He rather than H2as carrier gas, especially at high water vapor concentrations where rapid film growth can be obtained.

ISSN:0021-8979    

DOI:10.1063/1.351630

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Hydrogenated amorphous carbon films have been prepared from CH4, H2, and Ar mixtures by plasma‐enhanced chemical‐vapor deposition. Films with various physical properties were obtained from different deposition conditions. The deposition parameters varied included H2flow rates, Ar flow rates, total pressures, substrate temperatures, and power densities. Effects of each deposition parameter on the microstructures and the kinetics involved in the formation of each film are discussed. In addition, relations between deposition conditions, microstructures, and the optical properties are reported.

ISSN:0021-8979    

DOI:10.1063/1.351631

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have investigated the amorphous phase formation and initial crystalline reactions at Pt/GaAs interfaces via high‐resolution transmission electron microscopy (HRTEM) andinsituHRTEM. A 3‐nm‐thick amorphous intermixed layer consisting of three elements, platinum, gallium, and arsenic formed at the Pt/GaAs interface during the deposition of a 500‐A˚‐thick Pt film. The interlayer grew in a planar fashion in an amorphous state upon low temperature (e.g., 200 °C) annealing by a solid‐state amorphization reaction. This reaction occurs with a driving force of a negative heat of mixing, and by the dominant diffusion of Pt to the GaAs substrate, which was verified byinsituHRTEM. Following the growth of the amorphous interlayer, the Pt3Ga and PtAs2phases nucleated within the amorphous layer and grew at the Pt and GaAs sides, respectively. The relative mobility of the three constituents at the low temperature, the structure of the crystalline intermetallic compounds, and local thermodynamical equilibrium are responsible for the sequence of the crystalline phase formation. After a complete reaction at 400 °C for 20 min, we observed the formation of a layered structure of PtGa/PtAs2/GaAs as the final structure.InsituHRTEM experiments also demonstrated growth of the amorphous intermixed layer and crystalline reaction between the Pt film and the GaAs, which is consistent with the results from theexsituannealing treatment.  

ISSN:0021-8979    

DOI:10.1063/1.352347

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A study for the optimization of HgCdTe heterostructure lasers for applications as midinfrared wavelength sources has been carried out. Structures are examined to emit photons at 2.5 and 4.5 &mgr;m at 77 K. For the 2.5 &mgr;m case, it is found that a quantum‐well laser with well width of 200 A˚ in a separate confinement structure is optimum. For the 4.5 &mgr;m case the optimum structure is one with a 1000 A˚ active region. For the 4.5 &mgr;m case the high carrier density at threshold in quantum wells and the consequent high Auger rates do not allow the decrease of threshold current with smaller well sizes. This result is rather general for narrow‐gap zinc‐blende semiconductors and represents a cautionary warning against the commonly held belief that narrow quantum wells will always improve threshold currents.

ISSN:0021-8979    

DOI:10.1063/1.351632

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The supersaturation of interstitials during oxidation in pyrogenic steam at 900 and 1000 °C was determined through measurements of enhanced phosphorus diffusion. At 900 °C, the supersaturation during steam oxidation was found to be significantly less than that observed during dry oxidation at the same growth rate, and the interstitial supersaturation varied as the square root of the oxidation rate as predicted in previous work. At 1000 °C, interstitial supersaturation was similar to that observed in dry O2, and the interstitial concentration showed only a 0.25 power dependence on oxidation rate. It was also observed that the inert‐ambient annealing of an oxide deposited at low temperature resulted in enhanced phosphorus diffusion.

ISSN:0021-8979    

DOI:10.1063/1.351633

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report a new method of depositing amorphous hydrogenated silicon carbide (a‐SiC:H) at low substrate temperature in a plasma‐enhanced chemical vapor deposition reactor. By applying an external dc voltage to the rf‐excited powered electrode, we can shift the optimal deposition temperature from 250 °C to as low as 100 °C. We find thata‐SiC:H films deposited at positive powered‐electrode potential and low substrate temperature exhibit less microstructure, wider optical band gaps, and faster deposition rates than films deposited at conventional conditions.

ISSN:0021-8979    

DOI:10.1063/1.351634

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Thermally stimulated currents (TSCs) were examined in a temperature range from room temperature to 170 °C for positively corona‐charged polypropylene films which were, before charging, uniaxially cold drawn to different drawing ratiosDup to 3.5 or were annealed at different annealing temperaturesTaafter drawn toD=3. Two main TSC bandsP+1andP+2were observed around 60 and 140 °C, respectively. The peak temperature ofP+1strongly depended onDandTa: It shifted toward higher temperature by drawing while it turned to shift toward lower temperature by annealing.

ISSN:0021-8979    

DOI:10.1063/1.351635

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Measurements of mass flows of a dense gas‐solid suspension have led to a modification of the electrostatic probe theory. Previous ball probe theory based on dilute gas‐solid suspensions has been extended to account for the effects of multiple scattering and sliding when applied to a dense gas‐solid suspension. The validation of the theory was shown by the experimental results.

ISSN:0021-8979    

DOI:10.1063/1.351636

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A hole concentration greater than 1020cm−3in GaAs has been achieved using a liquid CCl4source for carbon in a low‐pressure organometallic vapor phase epitaxy system. The resistivity and hole mobility measured at 300 K for a heavily carbon‐doped (1.2×1020cm−3) Hall sample made from a thin (180 nm) epitaxial layer were 8.0×10−4&OHgr; cm and 65 cm2/V s, respectively. Carbon‐doped samples with excellent surface morphology were achieved using a V/III ratio of 22, and growth pressure and temperature of 80 Torr and 600 °C, respectively. A novel photoluminescence technique, based on band‐gap shrinkage of heavily dopedp+‐GaAs, has been shown to be useful for nondestructive measurement of the hole concentration in submicrometer layers.

ISSN:0021-8979    

DOI:10.1063/1.351637

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The charged state of bismuth atoms inn‐type bismuth‐modified amorphous thin films of Ge20Se80and As2Se3has been studied by x‐ray photoelectron spectroscopy. On the basis of the observed chemical shift, it is concluded that the Bi atoms in the modified films are positively charged. The charged Bi atoms perturb the equilibrium between positively and negatively charged defect centers, thereby causing a shift of the Fermi level towards the conduction band. The observed enhanced electrical conductivity and the conductivity conversion fromptontype in the modified films is the result of such a Fermi level shift.

ISSN:0021-8979    

DOI:10.1063/1.351638

出版商:AIP    

年代:1992

数据来源: AIP