摘要:

Hg0.80Cd0.20Te liquid phase epitaxial layers were grown at 502 °C on CdTe substrates. The cooling rate was varied from 0.15 to 1.32 °C/min, and the terrace surface morphologies were evaluated for all the liquid phase epitaxial (LPE) layers. The width of terraces was inversely proportional to the cooling rate. This result is explained by the increase in constitutional supercooling with increasing cooling rate. Composition of the LPE layer was uniform up to the surface except at the interface region. The composition profile did not depend on the cooling rate.

ISSN:0734-2101    

DOI:10.1116/1.574989

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Silicon carbide has been grown at 1100 to 1400 °C by chemical vapor deposition using CH3SiCl3and H2gaseous mixture onto a graphite substrate. The effect of deposition temperature, total system pressure, and the CH3SiCl3input fraction on growth characteristics and structure of deposits has been studied. The experimental results show that the SiC deposition reaction is a thermally activated process with the deposition rate limited by surface reactions. The apparent activation energy is about 26 kcal/mol at a system pressure of 200 Torr and decreases with the increasing total system pressure. In this experiment, polycrystalline β‐SiC always has been deposited. The preferred orientation of the deposited SiC films changes from 〈111〉 to 〈220〉 with increasing deposition temperature. The size of the polycrystalline β‐SiC grains becomes coarser as the deposition temperature and the CH3SiCl3input fraction are increased.

ISSN:0734-2101    

DOI:10.1116/1.574969

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The design and testing of a high ionization efficiency source for a partially ionized beam deposition (PIBD) system are described. The vaporized material from a crucible is partially ionized at the crucible exit, where the vapor has its highest density. The system can provide ionization efficiencies of up to 5% (ion/atom ratio) at ion energies ranging from 0.2 to 6 keV. Measurements of the ion current versus substrate bias potential along with the deposition rate are reported using Al as source material. A uniform ion beam intensity has been obtained over a 6‐cm‐diam substrate at a distance of 30 cm above the source. If the ionization source is placed a few centimeters away from the crucible, as it is in the conventional PIBD design, the ionization efficiency would reduce to<0.2% (ion/atom ratio). The reduction can be easily explained by geometry consideration.

ISSN:0734-2101    

DOI:10.1116/1.574977

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The slow release of reactive gases from the walls and electrodes of practical plasma enhanced chemical vapor deposition (PECVD) systems has been studied. These desorption effects become important when thin films with different compositions are sequentially deposited in single‐chamber deposition systems. The pressure rate of rise of a PECVD reactor was measured after exposure of the system to commonly used precursor gases. The nature of the gas, its pressure, the system temperature, and the time duration of the exposure are experimental variables. Contamination effects by dopants at the parts per million level were investigated by their effect on the electrical properties of subsequently deposited films. It is found that ammonia and diborane, both of which are extensively used for device fabrication, are especially difficult to remove from the system. Operational procedures such as long pumpout times, baking, and short exposure times to the gases, preferably at low pressures, can often reduce the extent of the carryover to an acceptable level in a single‐chamber system. However, the use of multichamber systems is likely to be the most effective solution to crosscontamination problems in PECVD processes.

ISSN:0734-2101    

DOI:10.1116/1.574997

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The gas density in front of a magnetron cathode has been found to be significantly reduced as a function of magnetron current. The reduction is due to gas heating and rarefaction resulting from collisions with the sputtered atoms ejected from the cathode surface. The density reduction is nonlinear with discharge current, and is sensitive to the sputter yield of the cathode, the average ejection energy of the sputtered atoms, the cross section for sputtered atom–gas atom collisions and the pressure, temperature, and thermal conductivity of the background gas. The process can be treated semiquantitatively in terms of heat conduction from the hot region near the cathode to the cold walls of the chamber. The presence and magnitude of this gas density reduction should have significant impact on the understanding of the plasma impedance, as well as the deposited film properties and the relative arrival rates for reactive depositions.

ISSN:0734-2101    

DOI:10.1116/1.574988

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The effects of mirror field application on ion energy and its dispersion for electron cyclotron resonance (ECR) microwave plasma stream are discussed. Low‐energy ions with minimal dispersion are extracted from ECR microwave plasma in the mirror field. Mirror field effects on the ion energy profile are caused by a decrease in plasma microparameter distribution, including plasma potential, electron temperature, and plasma density. A highly dense ion stream is extracted from ECR plasma with the mirror field.

ISSN:0734-2101    

DOI:10.1116/1.574990

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

The evolution of the interface formed between clean [N‐N‐(p,p‐oxydiphenylene) pyromellitimide] polyimide (PI) and evaporated gold was followed by high‐resolution x‐ray photoelectron spectroscopy (XPS). Overlayer and substrate core level emission behavior indicates the nucleation and growth of Au clusters on the PI surface. At low gold coverages (<1 Å nominal thickness), there was no observed interaction between the adatoms and the substrate. Above 1 Å we observe the growth of clusters on the PI surface and a shift of the Au 4fcore levels as the clusters become metallic. Significantly, we observe further shifting of the Au 4femission and the Fermi level at coverages greater than that expected for metallic behavior, and we see Au‐cluster‐induced broadening and shifting of the substrate core level spectra tolowerbinding energy. This unexpected behavior can be accounted for in terms of the injection and trapping of charge into the PI film from Au during the photoionization process. Angle‐dependent XPS results showed increased broadening and shifting near the surface, indicating that the amount of trapped charge was greater at the interface. This injection profile was modified by an annealing cycle of the Au/PI interface, as indicated by the coalescing of dispersed Au clusters and the partial recovery of the clean PI substrate characteristics.

ISSN:0734-2101    

DOI:10.1116/1.574991

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Dynamic time‐ and temperature‐dependent x‐ray photoemission studies of polyimide (PI) show the evolving valence bands and core level spectra, starting from partially polymerized PI and continuing through PI degradation at 500 °C. For temperatures below∼200 °C, we see little change, but curing above 300 °C is accompanied by changes in core level and valence‐band positions relative to the Fermi level. These changes are associated with the removal of defect induced states in the band gap of the polymer. Comparison of the valence‐band spectrum of the fully cured PI to recent electronic structure calculations shows good agreement. PI degradation occurs at temperatures between 450 and 500 °C, where there is a decrease in carbonyl and pyromellitic dianhydride benzene ring carbon 1semission due to loss of CO or CO2, and an increase in carbon atom density. Nitrogen 1sspectra exhibit the growth of new low binding energy components which indicate that the feature previously assigned to an isoimide structure is a metastable reaction intermediate of the degradation process. The oxygen 1sfeatures are primarily affected in the carbonyl oxygen peak, indicating ether oxygen bonds are more stable with respect to high temperatures.

ISSN:0734-2101    

DOI:10.1116/1.574965

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A new secondary‐ion mass spectrometry technique is described for the quantitative analysis and depth profiling of rare gases incorporated in thin films and bulk solids. A Cs+primary‐ion beam incident on the sample surface was used to produce sputtered (CsR)+(R=rare gas) molecular ions whose yield was proportional to the rare‐gas concentration in the analyzed region of the sample. Depth profiles have been measured for Ar and Kr implants in single‐crystal Si, Ge, and GaAs wafers and a Kr implant in polycrystalline Ni. Detection limits ranged from ∼4×1017cm−3for Ar in Ge to ∼1019cm−3for Kr in GaAs where the sensitivity was decreased due to interference with (Ga2As)+ions at mass 217. The Cs+primary‐ion current density used in these experiments was 6 mA cm−2. It was not possible to obtain sufficiently high Cs+current densities in our system to observe R+secondary ions, although they were detectable using an O+2primary ion beam incident at 35–40 mA cm−2. The high current densities required in the O+2experiments, however, resulted in a correspondingly high sputter etching rate and hence a decrease in the depth resolution. Measurements of secondary‐ion intensities as a function of primary‐ion current density and secondary‐ion energy distributions showed that (CsR)+molecular ions were formed by surface‐ionization processes, while R+secondary ions were formed primarily by inelastic gas‐phase collisions involving rare‐gas atoms released from the samples with thermal velocities.

ISSN:0734-2101    

DOI:10.1116/1.574966

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Measurements of electron stimulated desorption of CO+, CO+2, C+, and O+have been carried out for a sputter‐cleaned and annealed GaAs(100) surface exposed to CO2, O2, and NO at room temperature. The dependence of the ion yields on the incident electron beam energy from 0 to 200 eV exhibits thresholds at the Ga 3d, 3p, and 3sand As 3dand 3pcore level binding energies. The total desorption cross section for the ionic species is ∼10−18cm2.

ISSN:0734-2101    

DOI:10.1116/1.574967

出版商:American Vacuum Society    

年代:1988

数据来源: AIP