摘要:

The silicides of Pt (PtSi) and of Pd (Pd2Si and PdSi) were formed by the interaction of metallic thin films with single crystal substrates of Si. The stresses in the silicide films were measured at room temperature from the bending of the Si substrates, obtained via an x‐ray diffraction technique. The stresses vary approximately linearly with the heat treatment temperatures, without pronounced relationship with the different phase formations. For both Pd2Si and PtSi, the stress levels are correlated with the measured lattice parameter. Approximate values of elastic constants and expansion coefficients are derived.

ISSN:0022-5355    

DOI:10.1116/1.570486

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Al and Au interfaces with UHV‐cleaved CdS(101̄0) surfaces have been probed via soft x‐ray photoemission spectroscopy. We find that Al produces a highly localized reaction at the metal‐semiconductor interface, while Au promotes interface diffusion. These bonding differences appear to be characteristic of ionic semiconductor–metal interfaces in general.

ISSN:0022-5355    

DOI:10.1116/1.570487

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The effect of thermal annealing of CdSe and multilayer Cr/CdSe thin films has been studied by Auger spectroscopy and nuclear reaction analysis. Films with thicknesses from 0.05 to 0.3 μm were deposited by evaporation onto glass and platinum substrates and annealed for up to 120 min at temperatures between 240° and 400°C in flowing nitrogen. Auger spectra were obtained as the films were sputtered by 3 keV Ar+in a scanning Auger microprobe. There was no significant change in the composition of the CdSe films except when CdSe and Cr films were in contact. For example, Cr diffused through a 0.3‐μm overlayer in a few minutes at 300°C. There was an associated increase in the oxygen content of the film. This was confirmed by nuclear reaction analysis using16O (d,p)17O reaction. In the absence of Cr, there was no significant oxygen uptake. Diffusion profiles were obtained by Auger depth studies and an activation energy of 1.2±0.2 eV determined from the temperature dependence. Since Cr is ann‐type dopant in CdSe, the diffusion probably affects the electrical properties and, thus, may have an important effect on CdSe thin film transistors which use Cr as a source‐drain metallization.

ISSN:0022-5355    

DOI:10.1116/1.570489

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Thin film transistors (TFTs) are of current interest for addressing large‐area flat panel displays. In most cases, in‐vacuum mechanical masking and successive evaporations in a single pumpdown have been used to define the necessary patterns. While this has the advantage of minimizing contamination of the film interfaces, complex and expensive equipment is needed to fabricate high resolution patterns over large areas. We have, therefore, investigated the use of conventional vacuum deposition and photoengraving processes, similar to those used in silicon integrated circuit technology, and have successfully fabricated CdSe TFTs in which the gate and source‐drain levels have been defined by photoengraving. Al and Cr metallizations and Al2O3dielectric layers have been used. Well‐saturated transistors with switching ratios of ∠104and electron mobilities of ∠50 cm2V−1s−1are achieved only after the fabricated structure is thermally annealed. Since some thermal annealing appears to be essential in all of the reported TFT processes, the physical significance of thermal annealing has been investigated. A model involving activated diffusion is presented and the effect of different annealing conditions on transistor characteristics discussed.

ISSN:0022-5355    

DOI:10.1116/1.570490

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The epitaxial growth of silicon on (1̄012) sapphire by partially ionized vapor deposition is investigated with a RHEED–AES system. The measurement of the epitaxial temperature and the observation of the RHEED pattern during epitaxial growth are carried out under varying ionization conditions for the silicon ions; i.e., average ion energy of 30 and 180 eV and fractions of silicon ions mixed with silicon atoms ranging from 0 to 7%. When a silicon molecular beam is deposited without ionization for thickness from 2 to 10 nm, (100) oriented and two different {110} oriented islands are observed in the RHEED pattern at substrate temperatures between 870 and 1020 K. The RHEED pattern, however, shows no change for selective epitaxy when the silicon molecular beam is partially ionized up to 7%. A decrease in epitaxial temperature by as much as 150 K is observed at a fraction of silicon ions of 1%, but no further change is observed at higher fractions up to 7% for ion energies of either 30 eV or 180 eV.

ISSN:0022-5355    

DOI:10.1116/1.570491

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

A critical review of recent studies of the geometrical and electronic structure of the Si(001) and Si(111) surfaces is given. Emphasis is placed on low‐energy electron diffraction (LEED) studies of the geometrical structure, photoelectron spectroscopy studies of the electronic structure, and theoretical studies of the electronic and geometric structure of the Si(111)–(2×1), Si(111)–(7×7), Si(111)–(1×1)X, and Si(001)–(2×1) surfaces.

ISSN:0022-5355    

DOI:10.1116/1.570492

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The first determination of the atomic geometry of the (110) surface of InSb is reported. The structure is determined by comparing dynamical calculations of elastic low‐energy electron diffraction (ELEED) intensities with those measured atT=150 K. Initial candidate structures were obtained from an energy‐minimization calculation and from a kinematic analysis of room‐temperature ELEED intensities. Neither candidate proved fully compatible with the measured intensities so another search for the correct structure was performed using dynamical calculations. This procedure yields as the most probable surface structure for InSb(110) one in which the top layer undergoes both a rigid rotation of 28.8° and a 0.05 Å contraction toward the substrate. The Sb atoms move outward and the In atoms inward, giving a relative vertical shear of 0.78 Å in this uppermost layer. In the second layer, the In moves outward 0.09 Å and the Sb inward 0.09 Å. The resulting structure is analogous to that of covalently bonded GaAs(110) but different from that of ZnTe(110) which exhibits a more ionic bonding. We infer that highly covalent zincblende‐structure compound semiconductors exhibit reconstructions of their (110) surfaces characterized by (1) large bond rotations in the uppermost layer, with the anion moving outward and cation inward, (2) small bond‐length alterations (i.e., a few percent or less), and (3) distortions from the bulk geometry which penetrate at least two atomic layers in from the surface.

ISSN:0022-5355    

DOI:10.1116/1.570494

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The rotational relaxation of the GaAs(110) surface is considered. A cluster model is used fo simulating the crystal surface, and some quasi‐atoms are added in order to saturate the dangling bonds in the cluster boundary. The stable relaxation geometry of the GaAs(110) surface is determined by minimizing the total energy of the cluster calculated by the Extended Hückel Method. According to the calculation, a value of 18° for the tilted angle of the surface bond is suggested which is in fairly good agreement with that given by the partial yield photoelectron spectroscopy. The density of states for the cluster is also calculated, it is shown that for this relaxation model there are no empty cation states existing within the band gap.

ISSN:0022-5355    

DOI:10.1116/1.570495

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.570496

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The interfacial electronic states associated with Al and Ga overlayers on cleaved GaAs (110) surfaces are studied by ultraviolet photoemission spectroscopy (UPS) and low energy electron diffraction (LEED). Deposition of Al or Ga can produce valence‐band spectra nearly devoid of new structure. Sb produces quite significant changes in the surface valence band and is shown as a contrasting example. Pseudopotential calculations from the literature for Al‐ and Ga‐ordered overlayers are found to be in somewhat better agreement with the data than the corresponding tight‐binding calculations, particularly in the adatom states which lie above the GaAs valence‐band maximum (VBM), although neither calculation gives a good description of the observed overlayer states. It is shown that Al and Ga most likely form two‐dimensional clusters or rafts on the surface at submonolayer coverage which are not in registry with the GaAs surface lattice. A comparison is made with results by other workers for Al, Ga, and In on GaAs and Si.

ISSN:0022-5355    

DOI:10.1116/1.570497

出版商:American Vacuum Society    

年代:1980

数据来源: AIP