The interdirfusivity in artificial amorphous Si/Ge multilayers is found to be strongly dependent on the average composition of the films. The interdirfusivity of films with different average composition was determined from the decay of the first X-ray satellite. The nonlinear diffusion resulting from the composition dependence was observed by the evolution of the higher-order satellites.

Effects of the doping level of indium impurity on electrical and optical properties of the CdS thin films, prepared with solution-sprayed method have been studied. The density of free carriers can be raised to an order of magnitude higher than that of non-doped case by increasing doping level of indium up to 0.01mole-% while indium doping does not significantly change the mobility from its value in non-doped samples. The optical energy gap is decreased with increasing indium content while the thermal activation energy remains unchanged. The experimental results are discussed in terms of the self compensation and radiative recombination phenomena.

Thin film polymorphs of molybdenum trioxide have been synthesized by RF sputtering. Films deposited on thermally floating substrates are polycrystalline and exhibit preferred orientation. Depending upon the oxygen partial pressure maintained during sputtering, the films can be made to crystallize in either the thermodynamically stable orthorhombic a MoO3 form (unique 2D-layered structure) or the metastable monoclinic /3 MoO3 phase (3D ReO3-related structure). Metastable β films can be converted thermally to the a phase and the transformation appears topotactic. Films deposited on cooled substrates are amorphous. A correlation between the particular phase formed and adatom mobility is noted.

Time-resolved spectroscopy of the recombining exciton state in a highly strained II-VI semiconductor superlattice CdTe/ZnTe reveals strong localization effects at low lattice temperatures. Such phenomena originate naturally from small deviations in structural perfection on a monolayer scale in a strained superlattice with a small valence band offset. The quasi-2D aspect enhances the localization phenomena further.

Dopant elements, B and Ga, P, As and Sb, and Ge as well, have been implanted into thick (350–400 nm) layers of TiSi2 prepared by Ti-Si reaction. Both B and Sb appear to be immobile, this behavior is thought to result from very small solid solubilities, rather than from very small diffusion coefficients. The other elements display about the same behavior, with detectable grain boundary diffusion at temperatures as low as 600°C, and lattice diffusion becoming considerable at 750°C, so that with the cooperation of both phenomena almost complete homogenisation of these relatively thick layers occurs in 30 minutes at 800°C. Germanium is used in lieu of a Si radioactive tracer because it can be analyzed by Secondary Ion Mass Spectroscopy. Its behavior is thought to imply that there is little equilibrium adsorption of the dopant elements at the Si/TiSi2 interface. The comparable values of the diffusion coefficients for the mobile elements confirm the anticipation that the dopants move as substitutional atoms on the Si sublattice. Results obtained with some samples implanted with both dopant and Ti indicate that in these silicon-saturated suicide layers the diffusion process is not significantly affected by small changes in stoichiometry.

Refractory metal suicides have been used widely in VLSI fabrication, owing to their low resistivity, high-temperature compatibility, and oxidiz-ability. In this work, we have studied the titanium suicide formation, using a rapid thermal processor (RTP). Isothermal and isochronal sintering experiments were carried out to determine the appropriate process steps. The selective etch of the unreacted Ti was characterized. The sintered films were characterized by four-point probe, X-ray diffraction, and Auger electron spectroscopy. We also studied the oxidation at 800–1000°C of Ti suicide formed by sintering Ti and polycrystalline silicon using a RTP in N2 ambient. The oxidation results of Ti suicide formed using RTP in N2 ambient are compared with those formed using furnace sintering in vacuum/argon ambient and those deposited by cosputtering.

The technique of high resolution electron microscopy has been used to examine the structure of several multilayer systems (MLS) on an atomic scale. Mo/Si multilayers, in use in a number of x-ray optical element applications, and Mo/Si multilayers, of interest because of their magnetic properties, have been imaged in cross-section. Layer thicknesses, flatness and smoothness have been analysed: the layer width can vary by up to 0.6nm from the average value, and the layer flatness depends on the quality of the substrate surface for amorphous MLS, and on the details of the crystalline growth for the crystalline materials. The degree of crystallinity and the crystal orientation within the layers have also been investigated. In both cases, the high-Z layers are predominantly crystalline and the Si layers appear amorphous. Amorphous interfacial regions are visible between the Mo and Si layers, and crystalline cobalt suicide interfacial regions between the Co and Si layers. Using the structural measurements obtained from the HREM results, theoretical x-ray reflectivity behaviour has been calculated. It fits the experimental data very well.

Epitaxial CoSi2/Si multilayers have been grown on Si(111) substrates with up to four bilayers of suicide and Si. To our knowledge, these are the first reported epitaxial metal-semiconductor multilayer structures. The growth of these heterostructures is complicated by pinhole formation in the suicide layers and by nonuniform growth of Si over the suicide films, but these problems can be controlled through nse of proper growth techniques. CoSi2 pinhole formation has been significantly reduced by utilizing a novel solid phase epitaxy technique in which room-temperature-deposited Co/Si bilayers are annealed to 600–650δC to form the suicide layers. Islanding in the Si layers is minimized by depositing a thin (<100Å) Si layer at room temperature with subsequent high temperature growth of the remainder of the Si. Cross-sectional transmission electron microscopy studies demonstrate that these growth procedures dramatically improve the continuity and quality of the CoSi. and Si multilayers.

We have used cross-section and through-foil TEM, RBS, and x-ray diffraction to investigate reactions upon rapid thermal annealing of sputtered Ti-Si multilayers of various compositions and bilayer spacings. This study addresses the behavior of the Ti-Si interface at low annealing temperatures (T< 600δC) to determine the extent to which interdiffusion occurs prior to suicide formation, and to detect the formation of the first suicide at an early stage. Whereas most previous work studied a single Ti-Si interface, we have used multilayer films because a reaction occurs at many interfaces, allowing detection of a phase even if it is formed to a very limited extent.

The silicon layers in the as-deposited films are amorphous; the titanium layers are polycrystalline hep. The compositions of the samples are 40 at.% Ti, 60 at.% Si and 60 at.% Ti, 40 aL% Si, and the bilayer periodicity is about 10 nm. After a 30 second anneal at 455°C, significant interdiffusion occurs and we observed the formation of an amorphous Ti-Si alloy by interfacial reaction. The metastable disilicide, C49 TiSi2, nucleated along with a small amount of TiSi in the sample with higher silicon content (60%) upon annealing at 550°C for 10 seconds, but the amorphous alloy remained as the only product of reaction in the 40 at. % Si sample. Cross-section TEM of a sample fabricated at 60°C suggests that interdiffusion had begun during deposition of the films.

A Monte Carlo study of the growth of ZnSe by Molecular beam epitaxy is presented. The study is focused on the role of surface kinetic reactions on the structural quality of the epilayers. Two different models for the incorporation of Se molecules, one with a highly reactive physisorbed state and the other with a relatively nonreactive physisorbed state are employed for simulations. It is shown that the structural quality of the epilayers is very sensitive to the flux ratio if the physisorbed state is relatively nonreactive. It is also shown that if the physisorbed state is highly reactive, good quality epilayers are obtained over a wide range of flux ratio.

Transmission electron microscopy (TEM), was used to study the interfacial structure resulting from the alloying reaction of a Au/Ge/Au film on (100) GaAs. The metallurgical reaction at 400°C results in the previously unknown hexagonal Au3Ga phase. The crystal structure of the AuoGa phase is proposed based on the observed diffraction patterns and the lattice image The well-known fcchcp coherent jnterface is observed between Au and Au3Ga such that (111)Au // (0001)Au3Ga and [110]. // [1120]Au2Ga. In addition to Au3Ga, other Au-Ga compounds (Au7Ga2, Au2Ge), a Au-Ge metastabil phase, and a Au-Ge-As ternary phase were observed after annealing. After annealing above 400°C, epitaxially regrown GaAs crystallites on the underlying GaAs substrate were revealed by cross-section TEM. The current flows through these Ge-doped regrown GaAs regions and the contact becomes ohmic The size and density of the regrown GaAs crystallite increase with increasing annealing temperature between 400 and 500°C; this explains the decreasing tendency of contact resistance with increasing annealing temperature.

A high Schottky barrier contact is formed when amorphous Si-P solid solution film and p-type Si are brought into contact. Amorphous Si-P films were deposited by thermal decomposition of a Si2H6-PH3 mixture at 500°C. It was found that conductivity increases rapidly when PH3/Si2H6, is increased from 0.2 to 2. When PH3/i2H6 = 2, conductivity is 0.15 S/cm, and the dominant conduction mechanism is variable-range hopping. Barrier height of amorphous Si-P/p-type Si Schottky contact is estimated to be 0.8 – 0.85 V. This value exceeds the barrier height formed by any normal metal.

A systematic comparison of the growth of plasma deposited amorphous silicon a-Si:H on chromium and glass substrates using real-time ellipsometry is presented. In order to compare the optical properties of the substrates before and after a-Si:H deposition, the amorphous films are removed by H-etching. Although the early stage of the growth of a-Si:H on chromium substrates is compatible with a nucleation mechanism, chromium suicides are probably produced at the film substrate interface. A faster chemical reaction between a-Si:H and the glass substrate is observed.

We have made modulated solids consisting of several hundred layers of a-Fe80Zr20/a-Ni30Nb70 in which the layer thicknesses are a few nanometers. The modulating nature of the sample and the flat growth of the layers are confirmed by cross sectional TEM. The layers of a-Ni30Nb70 are non-magnetic and serve as inert layers separating the magnetic a-Fe80Zr20 layers. By varying the thickness of the a-FegoZr20 layers, the thickness dependence of the magnetic properties has been studied. The sign of the magnetic surface anisotropy constant has been determined.

Self-interstitial transport kinetics in float-zone and Czochralski silicon was studied during thermal oxidation of silicon membranes. Bulk recombination of interstitials is higher in the CZ than in the FZ silicon. The low apparent interstitial diffusivity obtained in this study is explained by a bulk effect.

Highly crystalline and resistive thin films of aluminum nitride have been rf magnetron sputter deposited. The films were characterized in terms of structure, electrical and optical properties. A perfect c-axis orientation along (002) direction was obtained, in the reactive sputtered films from a metal target, keeping the substrates as low as 350°C. The structural and electrical properties were observed to be sensitive to deposition conditions. It has also been observed that the combination of higher powers and low sputtering pressures, exposed the films to high energy neutral ion bombardment. A correlation between deposition parameters and the physical properties is presented.

High quality, β-SiC (111) monocrystalline films have been epitaxially grown via chemical vapor deposition at 1683K on hexagonal 6H αc-SiC (0001) using a (SiH4 + C2H4)/(H2) gas flow rate ratio of 1:3000. Cross-sectional transmission electron microscopy showed almost no line or planar defects at the film/substrate interface and a low density within the bulk of the film. Furthermore, high resolution transmission electron microscopy revealed a coherent β-SiC/α-SiC interface. Secondary ion mass spectrometry indicated that the diffusion of the Al in the substrate into the as-grown film was negligible. Unintentionally doped films are n-type with the carrier concentrations virtually always in the range of 1016-1017cm3, as determined by capacitance-voltage measurements. A gold-β-SiC Schottky diode having an ideality constant of approximately 1.6 was fabricated on the β-SiC epilayer.

We have grown a series of Ge and graded Si1-xGex epilayers on (100)Si substrates by MBE under different conditions. The quality of the layers has been characterized by cross-sectional TEM, Rutherford backscattering/ channeling and x-ray diffraction. This work addresses the optimization of growth temperature, (300–700°C) an evaluation of compositional grading, the effect of the incorporation of strained layer superlattice dislocation filters and post growth anneal cycles. Particular attention has been paid to grading GexSi1-x, x = 0 to 1 and the growth morphology of intermediate alloy epilayers.

Cantilever-beam measurements of ion-implantation induced stress in (InGa)As/GaAs, Ga(AsP)/GaP, and Ga(AsP)/GaAs strained layer superlattices (SLSs), grown either by molecular-beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD), have shown that a mechanism for precipitous stress-relief can be operative, f or room-temperature damage -energy deposition values above - 2 × 10 keV/cm. This phenomenon is correlated with the initial residual compressive stress on the composite structure and is determined by the differences in lattice parameter between the substrate and the buffer alloy-layer.

The effect of implant temperature, superlattice period, and directional diffusion has been studied for silicon impurity-enhanced compositional disordering of GaAs-AlAs superlattices (SL) of 9 ran and 16 nm period. The SL were implanted with Si at temperatures of 483 K, 293 K, and 77 K, with an energy of 100 keV and dose of 2.5 × 1014 cm-2. These were examined by cross-sectional transmission electron microscopy and secondary ion mass spectro-scopy for structural and compositional information. The damage due to implantation prior to annealing is strikingly less for superlattices than for bulk GaAs. All annealed samples exhibited disordering, with the 9 nm period SL exhibiting a deeper disordered region than the 16 nm SL. The greatest enhancement was found in the 9 nm period SL implanted at 77 K, in which the disordering extended from a depth of 25 nm to =300 nm. The mixing was found to be anisotropie, with the SL mixing propagating greater in depth than in the lateral directions. The result has important implications for high resolution patterning possibilities with this method.