Uma Venkateswaran Professor Ph.D., University of Missouri (Columbia) 186C Science and Engineering Building (248) 370-3423 venkat@oakland.edu venkat@oakland.edu

Publications Research Interests

Some Recent Publications:

High Pressure Raman Studies of polycrystalline BaTiO3, Phys. Rev. B58, 14 256 (1998).

Temperature-dependent Photoluminescence of In0.5Al0.5As/Al0.25Ga0.75As Self-organized Quantum Dots, J. Appl. Phys. 85, 2997 (1999).

Probing the Single Wall Carbon Nanotube Bundle: A Raman Scattering Study under High Pressure, Phys. Rev. B 59, 10 928 (1999).

High Pressure Photoluminescence Studies of Carbon-induced Germanium Quantum Dots grown on Si, Semicond. Sci. and Technol. 15, 155 (2000).

Pressure dependence of the blue luminescence in Mg doped GaN, Appl. Phys.Lett. 77, 2536 (2000).

Temperature Dependence of the Raman Scattering in HgBa2CuO1-x, Solid State Commun. 117, 685 (2001).

Effect of van der Waals Interactions on the Raman Modes in Single Walled Carbon Nanotubes, Phys. Rev. Lett. 86, 3895 (2001).

Pressure dependence of the Raman modes in iodine-doped single walled carbon nanotube bundles, Phys. Rev. B 65, 54102 (2002).

Diameter-dependent wall deformations during the compression of a carbon nanotube bundle, Phys. Rev. B 68, 241406(R) (2003).

Squeezing Carbon Nanotubes, U.D. Venkateswaran, Phys. Status Solidi (b) 241, 3345 (2004).

Research Interests:

Using two (tiny) diamonds for the jaws of a small vise-like device called the Diamond Anvil Cell, it is possible to generate extremely high pressures (on the order of a million atmospheres) on a microscopic sample held between the diamond anvils. We are interested in studying the laser light that is scattered off the sample to infer useful information regarding the electronic and vibrational energy levels in the sample. Using pressure and temperature as external perturbations, optical studies help in the characterization of new materials and in understanding their fundamental properties. The information obtained in experiments is used to test theoretical models and predictions.

Light scattering techniques such as photoluminescence and Raman spectroscopy are being used in our laboratory for the investigation of the optical properties of several technologically important materials. We have active collaborations with several research groups around the world. Photoluminescence from polymerized forms of solid C₆₀, heavily doped p-type GaAs and GaN, InA1As and C-induced Ge quantum dots have been studied under pressure (0-10 GPa) at low temperature (10 K). Raman studies on ferrelectric thin films of Ba(Sr)TiO₃ and carbon nanotubes have also been carried out. These studies have led to methods of reliable characterization for these materials grown using novel techniques and a better understanding of their optical properties.