Jason Simon, a 4th year PhD student, was selected to receive the Northrop Grumman Graduate Fellowship in Quantum Optics in August.

The Northrop Grumman Fellowship provides an outstanding opportunity for a talented UMBC Physics student to work with a global leader in defense technology while earning his/her PhD. Fellowship support totals $35,000, which includes an annual stipend, tuition and health care benefits, and some travel for one year.

Justin successfully defended his dissertation on August 25, 2008.

TITLE:
Initial HfO2 Growth on Si(100) and GaAs(100) Substrates using TEMAH+H2O and TDMAH+H2O ALD Processes

ABSTRACT:
Atomic layer deposition (ALD) is a cyclic growth process that is distinguished by a self-limiting, two-step surface reaction that results in precise growth control and high quality, conformal thin films. Due to the continuous downscaling of MOSFET devices, a large interest has recently developed in the ALD of high-κ dielectric materials as gate oxide layers on Si and III-V substrates. The ALD of HfO2 is an established process; however, there is still controversy over the initial growth mechanisms on differently prepared Si surfaces. This motivated a comparison of the nucleation stage of HfO2 films grown on OH- (Si-OH) and H-terminated (Si-H) Si(100) surfaces. Two different ALD chemistries are investigated, including tetrakis[ethylmethylamino]hafnium (Hf[N(CH3)(C2H5)]4), abbreviated as TEMAH, and tetrakis[dimethylamino]hafnium (Hf[N(CH3)2]4, abbreviated as TDMAH. H2O is used as the oxidizing precursor. Deposition temperatures of 250-275°C result in a linear growth per cycle of 1 Å/cycle. Techniques including Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and transmission electron microscopy are used to examine the film interface and initial film growth. HfO2 films are also subjected to post-deposition anneals, and the film morphology is examined with X-ray diffraction, Fourier transform infrared spectroscopy and atomic force microscopy.

GaAs MOSFET devices have long proven elusive due to the lack of a stable native oxide. Recent research into high-κ dielectric materials for use in Si-based devices has presented many new options for insulating layers on GaAs. HfO2 growth on GaAs(100) from a TDMAH+H2O ALD process is studied here. Three different GaAs surface treatments are examined, including buffered oxide etch (BOE), NH4OH, and a simple acetone/methanol wash (to retain the native oxide surface). Initial HfO2 growth on these surfaces is characterized with RBS and SE. The interfacial composition is examined with XPS both before and after HfO2 deposition. Also, an interesting native oxide ‘consumption’ mechanism is investigated, which involves the dissolution of the GaAs native oxide during the ALD process. This project presents the first detailed study of HfO2 growth on GaAs with the TDMAH/H2O ALD chemistry, providing XPS, RBS and SE characterization of early film growth.

Earth reflectances are highly anisotropic. The most anisotropic signal is observed over water surfaces where the glint effect generates a reflectance that varies by several orders of magnitude as a function of the observation geometry. Over land surfaces, the variations are not as large, but nevertheless significant. The reflectance of a given target varies with the observation geometry by a factor of up to four. This anisotropy causes some difficulties for a quantitative analysis of satellite measurement time series as the variability due to the changing measurement geometry may be as large as the geophysical signal that is monitored.

The POLDER/Parasol spaceborne instrument is a great tool to monitor these effects. Indeed, it provides up to 16 measurements of the same targets, with varying view angles, as the satellite flies over it. We will present and discuss the directional reflectance measurements, and the model that was developed to reproduce the observed signatures. The model is then used to correct the time series, for a much better identification of the geophysical signal, such as the vegetation dynamic.

Location: Physics Bldg., Room 401
Coffee: 3:15 p.m.

Chris successfully defended his masters thesis on August 27, 2008.

TITLE:
Laser System for the Fabrication of Toroidal Microcavities

ABSTRACT:
Toroidal micro-cavities have been shown to be one of the leading types of cavities for use in strong atom-cavity coupling. This property makes these cavities ideal for a range of applications from cavity quantum electrodynamics studies, to development of single photon sources, and quantum information technologies. The purpose of this project was to setup and test a laser facility for the final step in fabricating toroidal micro-cavities. The facility will later be used for production of these cavities for use in ongoing experiments within the UMBC Quantum Information Group.