Interfacial microstructure of In/Pd ohmic contacts to n-GaAs was studied by various X-ray diffraction techniques and secondary ion mass spectroscopy (SIMS). Analysis of this interface after various annealing showed that In1-xGaxAs compounds are formed at the interface and the composition of these compounds depends upon the annealing temperature. As the temperature increases, the stoichiometry of the Inrich compounds tends toward higher concentrations of Ga. The low contact resistance is achieved by dividing the Schottky barrier between metal and GaAs into two barriers due to metal/Inl-xGaxAs and In1-xGaxAs/GaAs. The barrier due to In1-xGaxAs/GaAs is believed to be the main limiting factor in lowering of contact resistance. The observed ohmic behavior for sample annealed at 500°C for 20 s is attributed to the further reduction of this barrier.

The initial phase formation sequence for reactions in cobalt/ amorphous-silicon multi-layer thin films has been investigated using a combination of differential scanning calorimetry, thin film X-ray diffraction, and transmission electron microscopy. Multilayer thin films with various overall atomic concentration ratios and various bilayer thicknesses were used in this study. It was found that crystalline CoSi is always the first phase to nucleate in the interdiffused amorphous layer which preexisted at the as-deposited coba It/amorphous-si licon interface. The CoSi nucleates at temperatures as low as about 530 K, but does not grow until the next phase, which is Co2 Si when excess Co is available, starts to nucleate and grow. The activation energy of the CoSi nucleation was found to be 1.-6±0.1 eV.

When thin films are deposited on substrates or when compound films are formed through interdiffusion of multi-film structures, intrinsic stress develops in the various films. Thermal mismatch between the expansion coefficients of the substrate and films in multi-film structures gives rise to extrinsic stress at elevated temperatures

By using Si<100> and rolled Al foil substrates supporting the same multi-film structure SiO2/Si/Co, the effect of extrinsic stress on interdiffusion of thin films is isolated.

Silicide growth is found to be inhibited (delayed) when formed on Al substrates compared to that formed on Si substrates. The delay in silicide growth is ascribed to delamination caused by large tensile stress prior to silicide formation. The growth rate of Co2Si is found to be similar on both Al and Si substrates

In this paper we report on the formation of compounds following the interaction of Pd with strained epitaxial layers of Si1−xGex (x=0.18) MBE grown on Si( 100), in the temperature range of 200 to 650°C. Compositional and structural analyses show that the dominant compound formed was an hexagonal ternary phase, Pd2Si1−yGey where the value of y is lower than of x, and varies with the reaction temperature. In addition to the ternary phase, the binary phase PdGe was also detected. The hexagonal compound grew in a textured manner with its c-axis oriented along the [100] direction of the Si1−xGex film. High temperature anneals (T≥550°C) resulted in the formation of a double layered structure, with the silicide/germanide compound layer on the surface, and below it a Ge rich epitaxial Si1−xGex layer. Strain relaxation of the unreacted layer occurred for specimens in which the double layer structure appeared (annealing temperature ≥550°C). A mechanism for the formation of the double layered structure is proposed.

High resolution and conventional transmission electron microscopy have been applied to study the interfacial reaction of yttrium thin films on Si. Epitaxial Ysi2−x film was grown on (111)Si by rapid thermal annealing at 500–1000 °C. The orientation relationship between yttrium silicide and (111)Si was determined to be [0001]Ysi2−x//[111]Si and (1010)Ysi2−x//(112)Si. The vacancies in the Ysi2−x film were found to be ordered in the Si sublattice plane and form an out-of-step structure. The range of M values of the out-of-step structure was found to narrow with annealing temperature and time. Defects along specific crystallographic directions were observed and analyzed to be intrinsic stacking faults.

A method is presented for calculating amorphization doses of ion implanted semiconductors, based on a continuous heterogeneous description of damage accumulation. This new approach is compared to the classical “critical damage energy density” (CDED) model. For high dose implantations the equivalence of both descriptions is formally established. It is proposed that the main limitation of the CDED model lies in the linear additivity of damage rather than the homogeneous damage build-up.

Crystallization of amorphous Si films on a glass substrate using Si+ ion implantation is investigated. 100keV and 180keV Si+ ion implantations into 600nm-thick amorphous Si layers crystallize half and almost all of the film thicknesses, respectively. This result demonstrates that crystallization by ion implantation, which contains both crystal nucleation and grain growth, is due to ion-solid interaction, and not to “pure” thermal effect by ion beam heating. Furthermore, two distinct regions are observed in transmission electron microscopy investigation of grain size at different depths of crystallized Si/SiO2 multi-layer specimens. The deep region below the projected range is composed of grains smaller than in the shallow region. This result is strongly related with crystal nucleation and growth kinetics by ion implantation.

The effect of substrate nature on the solid phase crystallization at 600 °C of a-Si deposited by low pressure chemical vapor deposition is investigated by x-ray diffraction and transmission electron microscopy. The nucleation rate varies slightly resulting to a weak variation in the final grain sizes as a function of the substrate type. In all cases the grain growth mode is found to be three dimensional. In contrary, a drastic effect of the substrate is observed for films deposited by plasma enhanced CVD. Fast crystallization is obtained on indium tin oxide (ITO) resulting to small grain poly-Si, whereas the crystallization is retarded on glass leading to an increase in the grain size.

Amorphous and microcrystalline films of silicon and silicon carbide have been deposited by means of PECVD at low substrate temperature (200°C), with reactive gases highly diluted in H2. Devices quality a-Si:H films have been annealed in vacuum at temperatures in the range 200- 1000 °C. The transition from amorphous to crystalline structure was studied by X-ray, Raman and I.R. spectroscopies, optical analysis in UV-VIS-NIR region, Transmission Electron Microscopy, Differential Scanning Calorimetry and Electron Spin Resonance measurements. By comparing the results of the two methods to obtain microcrystalline films we have deduced information on the process of growth of Si and SiC microcrystals.

The crystallization of amorphous Si in a Al/Si multilayer (with a modulation length of about 120Å) was investigated using transmission electron microscopy, differential scanning calorimetry and X-ray diffraction. Amorphous Si was found to crystallize at about 175 °C with the heat of reaction of 11±2(kJ/mol). Al grains grow prior to the nucleation of crystalline Si. The crystalline Si was found to nucleate within the grown Al layers. The incipient crystalline Si initially grows within the Al layer and then spreads through the amorphous Si and other Al layers. Because of extensive intermixing, the original layered structure is destroyed. The Al(111) texture is also enhanced.

The phase transformation of amorphous silicon-aluminum thin films with 16 at.% and 30 at.% aluminum was characterized by TEM during an in-situ anneal at 500°C. No crystallization was observed in the samples having 16 at.% Al even after a 10 hour anneal at 500°C. In contrast, nucleation of crystallites was observed in the samples having 30 at.% Al after a 40 min anneal. The size of these crystallites grew during annealing. Single crystal regions were also observed and were identified as aluminum having <111> orientation.

To successfully implement Silicon-on-Insulator (SOI) technology using polysilicon-on-oxide, it is necessary to maximize the grain size such that the active devices are entirely within very large single crystal grains. A drastic increase in grain size in polysilicon has been reported due to secondary grain growth in ultra-thin, heavily n-type doped films upon regular furnace annealing. Very little work has been undertaken, however, to study secondary grain growth during Rapid Thermal Annealing (RTA).This paper is a study of the grain growth mechanism in heavily P-doped, amorphous silicon films during RTA. Secondary grains as large as 16 μm have been obtained in 160 nm thick films after a 180 s RTA at 1200 °C, representing a grainsize- to-film-thickness-ratio of 100:1. This is the largest secondary grain size and grain-size-to-film-thickness reported in the literature. A detailed analysis of negatively charged silicon vacancies has also been employed to explain the lower activation energy (1.55 eV) of secondary grain growth compared to that of normal grain growth (2.4 eV).

The surface texture of polysilicon films, used for capacitor storage nodes, have been investigated for various deposition conditions. An increase in capacitance of approx. 70% has been observed in this work. The reproducibility of the surface texture and the resulting capacitance can be improved by optimizing the deposition pressure. The gain in capacitance was also observed to be affected by the thickness of the film. In the mass flow controlled regime the increase in capacitance was 12%. The increase in surface roughness and the gain in capacitance for the hot wall process provides a simple alternative for satisfying the charge capacity requirements in high density dynamic random access memories.

We report the results of our study of controlled interface roughness in low-order GaAs/AlAs superlattices. Samples were prepared using either the interrupted growth or the migration-enhanced epitaxy (MEE) technique. The samples were prepared with m atomic planes of GaAs and m atomic planes of AlAs (m × m) per modulation wavelength and repeated p times. For this study, m = 1 or 3. The samples were studied using X-ray diffraction. The interrupted growth samples both showed a split in one diffraction line indicating layers were not of integral order while the MEE samples showed no splitting, indicating integral order layers.

In this work we examine the physical properties for the superlattice system (GaAs)n1 (AlAs)n2/GaAs(100) for low values of n1 and n2, i.e., n1 = n2 = 3, 6, 12. Normal, interrupted growth, and migration enhanced epitaxy (MEE) growth techniques were used to grow the superlattice structures in a molecular beam epitaxy system. X-ray diffraction spectra were obtained, and the major and satellite peak positions were analyzed to obtain the superlattice periodicity. An analysis of the major diffraction peaks and their associated satellites produced superlattice periodicity in good agreement with theory. Diffraction peaks were also observed in regions adjacent to the primary diffraction peaks which did not occur in the expected satellite positions. An analysis of these peaks relative to the primary peak indicate periodicities corresponding to layer thickness greater than the intended period. One possible cause for these periodicities is growth conditions that exist during the growth of the superlattice which result in the deposition of fractional monolayers. In this study we present results which suggest that an arsenic-deficient growth condition may be a contributing factor in the deposition of fractional monolayers.

A new time-resolved x-ray method of probing the kinetics of interfacial strains in semiconductor heterostructures is presented. High-resolution synchrotron radiation measurements of the strain relaxation during rapid thermal annealing (RTA) show that the lattice strain of an as-grown strained layer structure GaAs-Inx.Ga1−x-As-GaAs/GaAs is relieved cooperatively by a series of sluggish discontinuous transitions. We find that ion implantation enhances the annealing kinetics of InAlAs strained layers.

We report an epitaxial growth of TaSe2, a family of transition metal dichalcogenides that exhibit Charge Density Waves (CDW). The films that have been characterized with RHEED, LEED, XPS and STM showed two different phases. Occurrence of CDW in the ultrathin films has been detected by XPS and LEED.

The science and technology underlying phase change reversible optical storage, with an emphasis on the media, are reviewed. The transformation kinetics and their effect on writing (amorphization), erasing (crystallization) and long-term data stability are discussed. Phase separation is shown to affect cyclability and cause increased media noise. A readback CNR of 65.0 db was obtained by eliminating grooves as a source of media noise and using a recording layer which crystallizes into a cubic phase. Recording performance at short wavelengths is discussed.

The crystallization properties of Te-Ge and Te-Ge-Sb alloys prepared by thermal evaporation were analyzed using various characterization techniques. Similar to previous results, our data for Te-Ge shows that alloys that deviate slightly from Te50Ge50 stoichiometry show drastically slower crystallization kinetics. Raman spectroscopy and x-ray diffraction show that alloys having non-stoichiometric atomic ratios phase separate during crystallization into a Te50Ge50 phase plus pure crystalline tellurium or germanium. It is this relatively slow process of phase segregation which limits the crystallization rate. Phase segregation during crystallization of non-stoichiometric Te-Ge can be eliminated by adding antimony to samples having a tellurium concentration of from 45 to 55 atomic percent over a wide range of Ge:Sb ratios. These alloys can have laser induced crystallization times of less than 50 nsec. The thermal crystallization temperature is reduced only slightly when antimony is substituted for germanium.

Significant point defect injection during a pulsed laser melt process is reported for the first time. Heteroepitaxial InxGa1-xAs/GaAs layers fabricated by a pulsed laser induced epitaxy technique are used in this study. Transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) and secondary ion mass spectrometry (SIMS) are employed to study the redistribution behavior of each species on the atomic scale. It is found that both the Si dopant species and the Ga, As, and In host atoms are injected into the underlying GaAs substrate. These species are then significantly redistributed, forming near spherical As-rich regions. Direct evidence of Asi and Gai (Ga and As interstitialcies) profiles in the GaAs substrate are also obtained for the first time. A hypothesis, based upon the combined effects of concentration impulse and large temperature gradients across the liquid-solid interface, is proposed to explain the significant solid phase diffusion observed during the pulsed laser melting process. We estimate the temperature gradient induced electric field during the process to be on the order of 104V/cm.