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The primary scientific contributions in this area are related to investigations of dynamic light-matter interactions when a growing thin film is simultaneously irradiated with a nanosecond (ns) pulsed laser. We  have shown that light-matter interactions mediated by a substrate surface permits  thermal effects and leads to significant nanoscale control of film morphology. (Click here for a comprehensive paper in J. Phys. D: Appl. Phys)  

The primary scientific contributions in this area are related to materials for non-linear switching and multi-wavelength information processing. For non-linear switching, our work has focussed on the interplay of composition and microstructure that minimizes optical loss to make efficient switches (see our recent APL paper here). For multi-wavelength processing, we have focused on predicting the physics of plasmonic behavior in multi-component nanocomposites. (Click here for our recent PRB paper on this topic).

Correlation of structure with processing conditions as well as with electronic properties is essential to build complex systems. We are interested primarily in the correlation of length scales, dimensionalities and nano/micro-structure on properties. Some examples of work in this area are provided:

Ion implantation: An extensive study has been performed on vacancy-defect production in Si following high-energy ion implantation. The vacancy-implanter was quantified using the Au-labeling teachnique. This technique proved extremely useful towards the low-temperature activation of B in Si, which resulted in a patent. (Click here for a paper)

Buried defects:   Experiments and Monte Carlo simulations of damage production via high-energy implantation in Si/X-type structures (where X refers to a buried film) show that the nature of the defects at the front Si/X interface can be changed from vacancy to interstitial-type by increasing the mass of atoms in the buried thin-film, X. These experiments provide quantitative verification of nonuniform defect production at an ion-irradiated buried interface in Si. (Obtain the paper here)

Indirect-gap semiconductors: When a dc-electric field is applied to indirect  band-gap semiconductors, the linear absorption coefficient has an exponential tail below the band edge reminiscent of the tunneling effect and the   development of an oscillatory behaviour (Franz-Keldysh oscillations) above the fundamental absorption edge E_g. We have developed a theory to express nonlinear TPA under dc fields. One of the key  results of our formalism is the universality of the Franz-Keldysh effect with respect to a rescaled energy gap given by E_g/N, where N is the number of photons   involved in the process. This study is important because TPA places limitations on the use of indirect  gap semiconductors like Si and Ge in optical switching applications. (Obtain paper here)
 
Magnetism: Role of size on domain behavior in magnetic structures created by various means, including thin film self-assembly and from amorphous alloys. (Publications in preparation)

 

This research focusses on physical vapor deposition by laser ablation on microstructure of multi-elemental systems including metals, ceramics  (oxides and borides) and metallic glasses. Some examples include:

Metal deposition on high-aspect ratio structures: Experiments and atomistic simulations of metal growth on sidewalls and trenches were performed. Examination of the film microstructure and morphology resulting from the simulations indicated that the energetic impinging particles are necessary to produce film densities comparable to those found experimentally. By including these effects, good agreement between the simulations and the experimental results were obtained. (See paper here)

Depth-graded multilayers for X-ray mirrors: We describe the development of depth-graded W/Si multilayer films prepared by magnetron sputtering for use as broad-band reflective coatings for hard x-ray optics. (see paper here)

Role of Ag on YBCO Growth:  We determined that Ag mixed into a YBCO target results in enhanced oxygenation and grain growth of YBCO films. (see paper here)

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