Nanometer-scale Material Processing and Characterization for Emerging Information Technologies: Studies of InAs and Diamond

Abstract

The demand for high-performance information processing capabilities continues to grow rapidly. Conventional information processing technologies rely primarily on silicon-based electronic devices, such as complementary metal-oxide-semiconductor (CMOS) devices. However, fundamental limitations imposed by quantum mechanical effects constrain further performance improvements in functional silicon electronics. To meet future information processing needs, emerging technologies based on semiconductor materials beyond silicon, such as indium arsenide (InAs) and diamond, have been proposed. While promising, these technologies remain far from maturity for practical application. A key challenge lies in the precise control of material properties at the nanometer scale. Specifically, physical and chemical properties at material surfaces, interfaces, and defect sites within the bulk must be thoroughly characterized and controlled. Achieving such control is essential for improving the performance, reliability, and scalability of next-generation information technologies.This dissertation addresses the overarching goal of controlling material properties at the microscopic scale through three research topics: (1) the correlation between surface electronic properties and surface oxide chemistry of InAs, (2) the growth and characterization of micrometer-sized diamond crystallites, and (3) the engineering of point defects within the diamond lattice. For the first topic, the correlation between surface electronic properties and native oxide chemistry at the InAs surface was investigated using X-ray photoelectron spectroscopy (XPS). Extended XPS measurements were conducted on the InAs surface with stable native oxides. The evolution of chemical composition of native oxides, distribution of chemical states at the surface, and changes in surface band bending was monitored and systematically analyzed. The observed concurrent evolutions were interpreted to reveal modifications in the atomic bonding network of the surface oxide layer. The results suggest that the electronic properties of the InAs surface are strongly influenced by arsenic oxide chemistry, where interface bond distortions and trapped positive charges within the oxide network are proposed to play a critical role. For the second topic, methods for improving the crystal quality of micrometer-sized diamond crystallites grown on foreign substrates were explored and understood. Substrate surface pretreatment techniques and chemical vapor deposition (CVD) process conditions were developed for diamond nucleation and growth on silicon substrates. Characterization of the pretreated substrates revealed that modifications to substrate surface morphology, induced by mechanical abrasion and hydrogen plasma treatment, play a critical role in controlling the ratios of diamond and non-diamond carbon phases during nucleation. Analysis of the resulting diamond crystallites showed that reducing the graphitic carbon fraction is accompanied by an increase in internal lattice strain, highlighting a trade-off in minimizing defect- and strain-related sources for the decoherence of embedded color center qubits. For the third topic, methods for the selective engineering of point defects within the diamond lattice were developed and analyzed. Ultraviolet nanosecond laser pulses were used to irradiate a single-crystal diamond sample under vacuum. The resulting defect structures were characterized using confocal photoluminescence (PL) spectroscopy. These laser pulses were found to selectively modify a self-interstitial-related defect without affecting the background nitrogen-vacancy (NV) centers. By systematically varying laser parameters, the interaction between the laser pulses and the diamond lattice was investigated in detail. Bond modifications induced by electronic excitation were proposed to explain the observed effects. These results provide proof-of-concept that nanosecond laser writing offers a powerful approach for deterministic control of diamond color centers for quantum applications.