ZrO2/Ge is potential high-k dielectric candidate to replace silicon based devices. Controlling stress in zirconia film and stabilizing high dielectric constant phase is crucial for high-k application. A precise control of stress and phase selectivity in high-k thin films is demonstrated. Thin films of ZrO2 were grown by reactive sputter deposition. Wide range of growth stress in thin films from -0.3 to -2.8 GPa can be tuned by growth rate control. Adatom incorporation into grain boundary was the dominant source of observed stress. Phase selectivity in zirconia was achieved by tuning growth parameters.

Unique cocoon- and rod-shaped alpha-phase ferric oxide, hematite (α-Fe2O3) is prepared by a simple, scalable and surfactant-free chimie douce synthesis. The structure and morphology is confirmed by x-ray diffraction, field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The electrochemical properties of α-Fe2O3 anodes are investigated using cyclic voltammetry, galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. The mesoporous α-Fe2O3 exhibited an initial discharge capacity >1741 mAh/g with excellent cycling performance and rate capabilities. The solvent used for the preparation of α-Fe2O3 plays a key role in determining the morphology of the materials, which greatly influenced its electrochemical properties.

Ultra-thin flakes of layered materials have recently been attracting widespread research interest due to their exotic properties. In this work, we study the optoelectronic response of a hybrid of two such materials – graphene and MoS2. Our devices consist of mechanically exfoliated graphene flakes transferred on top of similarly exfoliated MoS2. The electrical response of the hybrid is studied in the presence of white light. We show that the four-point resistance of graphene is modulated in the presence of light. This effect is observed to be a strong function of gate voltage. We have also extended our studies to CVD (chemical vapor deposition) - grown graphene transferred onto MoS2 which show qualitatively similar features, thereby attesting to the scalability of the device architecture.

We have studied the evolution of stress and microstructure of compositionally graded Al1-xGaxN (0 ≤ x ≤1) buffer layers on (111) Si substrates with varying thicknesses. In-situ stress measurements reveal a tensile-to-compressive stress transition that occurs near the half-thickness in each buffer layer. Cross-sectional transmission electron microscopy (TEM) shows a significant reduction in threading dislocation (TD) density in the top half of the buffer layer, suggesting that the compressive stress enhances the threading dislocation annihilation. The composition of the buffer layers varies linearly with thickness, as determined by X-ray energy dispersive spectrometry (XEDS). The composition grading-induced compressive stress offsets the tensile stress introduced by microstructure evolution, thus yielding a tensile-to-compressive stress transition at x ≈ 0.5.