We have developed a methodology aimed at accurately determining the various forms of energy transfer(convective loss, radiative loss and absorption of lamp energy by the wafer)occurring in any advanced RTP system, based on basic system identification experiments and simple 3- dimensional physical model depicting the heat transfer processes. The identification experiments help in estimating the uncertain system dependent factors which characterize the various forms of energy transfer, which may be otherwise difficult to calculate on pure theoretical basis. This methodology forms the basic building block of our effort to develop a tool which can predict the temperature distribution across the wafer in a realistic way. This tool can be used both as a wafer temperature control algorithm in any advanced RTP system by incorporating more accurate system impedance parameters(convective and radiative loss) as well as by an end user to calculate the required power level settings to various lamp zones to attain reasonable temperature uniformity for a RTP system which does not have a dynamic con-rol.

The kinetics of the C49 to C54 TiSi2 phase transformation in nitrogen ambient have been investigated in a temperature range from 700 °C to 800 °C for a range of titanium film thicknesses (135 Å to 350 Å) using sheet resistance measurement, Auger electron spectroscopy(AES), Rutherford backscattering spectroscopy(RBS) and transmission electron microscopy(TEM). About 80% of the titanium converts to titanium silicide with the rest converting to titanium nitride. The activation energies obtained for the C49 to C54 transformation in nitrogen ambient are lower, at least by 2–2.25 eV, than that obtained for the transformations occuring either in argon ambient or vacuum environment. This has been explained with a model involving stress state of titanium silicide film with titanium nitride overlayer.

We have developed a methodology aimed at accurately determining the various forms of energy transfer (convective loss, radiative loss and absorption of lamp energy by the wafer)occurring in any advanced RTP system, based on basic system identification experiments and simple 3-dimensional physical model depicting the heat transfer processes. The identification experiments help in estimating the uncertain system dependent factors which characterize the various forms of energy transfer, which may be otherwise difficult to calculate on pure theoretical basis. This methodology forms the basic building block of our effort to develop a tool which can predict the temperature distribution across the wafer in a realistic way. This tool can be used both as a wafer temperature control algorithm in any advanced RTP system as well as by an end user who is equipped with a not so advanced, but multizone, RTP system( the one with the user defined power levels to various zones).

We have fabricated Ni3Al and NiAl thin films on different substrates by the pulsed laser deposition (PLD) technique. A high energy nanosecond laser beam was directed onto Ni–Al (NiAl, Ni3Al) targets, and the evaporated material was deposited onto substrates placed parallel to the target. The substrate temperature was varied between 300 and 400 °C, and the substrate-target distance was maintained at approximately 5 cm. The films were analyzed using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectrometry. At energy densities slightly above the evaporation threshold, a slight enrichment of Al was observed, while at higher energy densities the film stoichiometry was close (<5%) to the target composition. Barring a few particles, the surface of the films exhibited a smooth morphology. X-ray and TEM results corroborated the formation of Ni3Al and NiAl films from similar target compositions. These films were characterized by small randomly oriented grains with grain size varying between 200 and 400 Å.

Good quality ceramic thin films of yttria-stabilized zirconia (YSZ), MgO, BN and TiN were grown on single crystal silicon with (100) orientation using in-situ pulsed laser physical vapor deposition (LPVD) technique.Laser deposition parameters were optimized and the resulting thin films were characterized by X-ray diffraction ,Rutherford backscattering spectrometry and transmission electron microscopy (plan and cross section). All the films were found to be polycrystalline with a texture. The absence of interfacial reaction and smooth interface on the atomic scale are the main features observed in these oxides and nitrides thin films on Si (100) substrate.

We have studied and analyzed critical thickness required for the formation of misfit dislocations in semiconductor heterostructures. The present analysis has been carried out assuming that the nucleation of a misfit dislocation is controlled by the activation energy. The energy of the cohernt interface and the misfit dislocation configuration has been evaluated using a discrete dislocation analysis. Further, atomic structures of coherent and semicoherent interfaces containing misfit dislocations of the type a/2<110={111} ↑ <110= (600 dislocation), a/2<110={001} ↑ <110= (90° dislocation) and a/6<112={111} ↑ <110= (90° partial dislocation) in Ge/Si system were simulated. The total energy, consisting of both core and elastic energy components, was calculated using Stillinger-Weber interatomic potentials. The results show that the energy is a strong function of the nature of dislocations. A 60° dislocation is found to exist in undissociated form in shuffle configuration, but the core contains a dangling bond at the interface. The core of a 90° dislocation reconstructs at the Ge/Si interface with no dangling bonds. The calculated atomic configurations of dislocations and interfaces are found to be in good agreement with high resolution transmission electron microscopy observations.

Excellent quality epitaxial and textured superconducting HoBa2Cu307.x (Ho 123) thin films have been fabricated on lattice matched (100) KTaO3 and (100) LaAlO3, and lattice mismatched (100) MgO substrates by the pulsed laser evaporation (PLE) technique. A bulk Hol23 target was evaporated using nanosecond excimer laser pulses with the evaporating material depositing on a substrate maintained in the temperature range of 550‐650°C. The temperature for zero resistance for HoBa2Cu3O7_x films deposited on various substrates at 650°C varied between 85 to 89K. The epitaxial films deposited on (100) LaA103 substrates exhibited critical current densities greater than 3.5 x 106 Amps/cm2 at 77 K. The superconducting properties of the Ho 123 films were found to be similar to Y123 films.

We report in‐situ fabrication of c‐axis textured YBa2Cu3O7‐x superconducting thin films with Tco > 77K on unbuffered silicon substrates by the biased pulsed laser evaporation (PLE) technique in the temperature range of 550‐650°C. At substrate temperatures below 550°C, no c‐axis texturing of the superconducting film was observed. The YBa2Cu3O7‐x superconducting films were fabricated by ablating a bulk YBa2Cu3O7 target by a XeCl excimer laser (λ = 308 nm, τ = 45 × 10‐9 sec) in a chamber maintained at an oxygen pressure of 0.2 torr . The thickness of the films was varied from 0.3 to 0.5 nm depending on the number of laser pulses. Extensive diffusion was observed in thin films deposited at substrate temperatures above 550°C. However, microstructurally, with increase in the substrate temperature the films exhibited larger grain size and greater degree of c‐axis texturing (measured by the ratio of the (005) and (110) X‐ray diffraction peaks). This was found to give rise to better superconducting properties with Tco exceeding 77 K for YBa2Cu3O7‐x films deposited on Si substrates at 650°C.

The formation of superconducting thin films on lanthanum aluminate substrates is very important for high‐frequency applications. In this paper, we discuss the fabrication of epitaxial superconducting YBa2Cu3O7 thin films on (100)LaAlO3 substrates, which exhibit excellent dielectric properties required for high frequency applications. The films were deposited by the biased pulsed laser evaporation technique (PLE) at substrate temperatures between 500‐650°C and exhibit excellent crystallinity with best minimum ion channeling yields corresponding to approximately 3%. The superconducting transition temperatures varied from 88‐92 K with critical current densities at 77K and zero magnetic field greater than 4 ‐ 5 x 106 Amps/cm2.

We have investigated the formation of various multilayer thin films by the laser physical vapor deposition technique. A multi stage target holder was constructed to perform all process steps in-situ; target/substrate cleaning, deposition, and annealing. The laser physical vapor deposition technique offers many advantages over conventional physical vapor techniques, such as, lower substrate temperature, microstructural control, and very low contamination levels. Film thickness can be controlled from near atomic to micron dimensions. A layer-by-layer (two dimensional) growth can be achieved, resulting in nonequilibrium structures. The films were analyzed using cross-section and high resolution transmission electron microscopy (TEM). The significant reduction in substrate temperature for the formation of high quality multilayer and epitaxial films opens up many new areas of applications requiring reduced thermal-budget processing.

Defects such as dislocations and interfaces play a crucial role in the performance of heterostracture devices. The full potential of GaAs on Si heterostructures can only be realized by controlling the defect density. The reduction of threading dislocations by the use of strained layer superlattices has been studied in these heterostructures. Several superlattice structures have been used to reduce the density of threading dislocations in the GaAs epilayer. The use of strained layer superlattices in conjunction with rapid thermal annealing was most effective in reducing threading dislocation density. Transmission electron microscopy has been used to study the dislocation density reduction and the interaction of threading dislocations with the strained layers. A model has been developed based on energy considerations to determine the critical thickness required for the bending of threading dislocations.

The nucleation and glide of misfit dislocations in GaAs/Si system is investigated using transmission electron microscopy. GaAs epilayers of different thicknesses were examined by electron microscopy (plan and cross-section) and the elastic strain remaining in the film has been related to the average spacing of the misfit dislocations at the interface. A model is developed based on minimum energy considerations to determine the strain-thickness relationship. The theoretical predictions of strain relaxation are compared with experimental observations using high resolution electron microscopy.

We have calculated stress distribution and critical thickness for the growth of strained epilayers having various values of mismatch between the epilayer and the substrate. The present analysis has been carried out assuming that the nucleation of a misift dislocation is controlled by the activation energy. Further, a misfit dislocation is nucleated when the areal strain energy density of the coherent film exceeds the activation energy associated with the misfit dislocation configuration. The latter term has been deternmined using the discrete dislocation method in conjunction with a surface dislocation analysis. The surface dislocation configuration is obtained by minimizing the total energy associated with the two-phase medium. It is verified that the free surface boundary conditions and the continuity of stresses acrosss the interface are satisfied by the surface dislocation array. These energy calculations are expected to be more accurate than those performed by previous workers.

We have calculated the stress distribution and critical thickness for the growth of strained epilayers having various values of misfit between the epilayer and the substrate. During formation of epitaxial films, the growth (pseudomorphic) occurs upto a certain thickness with planar spacing normal to the interface being essentially the same both in the substrate and the film. Above a critical thickness it becomes energetically favorable for the film to contain dislocations. This occurs usually by generating glide dislocations near the free surface because there is a lack of dislocation sources in mostly “defect-free” semiconductor materials. We present an analysis of the critical phenomena in semiconductors based upon this experimental fact. In all the previous analyses, the critical step associated with the generation of dislocations was neglected. We also consider finite (island) growth of thin films and its effect on critical phenomena. The experimental results show the presence of glide dislocations in Ge/Si with the extra half planes in silicon substrate.