Final Report for Aoard Grant Fa4869-08-1-4011 Title: Study on Locally Confined Deposition of Si Nanocrystals in High-aspect-ratio Si Nano-pillar Array for Nano-electronic and Nano-photonic Applications "

In this project, versatile processing techniques are established for improving the internal and external quantum efficiencies of Si MOSLEDs via the detuning the size and density of high-aspect-ration Si nano-rod and buried Si nanospheres. A rapid thermal annealing synthesis of metallic nanodot array is realized to control the size and density control of metallic nanodots as an etching mask for obtaining Si nano-rod or nano-pillars. Afterwards, the induced-couple-power reactive ion etching (ICP-RIE) of metallic nanodot masked Si substrate is performed for high density and aspect-ratio Si nano-pillar array formation. The localized PECVD deposition of Si nanospheres within Si nano-pillar array is achieved under high deposition-temperature and low plasma-power circumstances. The current-voltage, Fowler-Nordheim tunneling, and EL characteristics of the MOS light emitting diodes made on Si nano-pillar roughened p-Si surface is analyzed. Microwatt light emission from MOSLED made by using SiOx film with buried Si nanocrystals on Si nano-pillar array is demonstrated. The Si nano-pillar array obtained by drying the rapidly self-aggregated Ni nano-dot masked Si substrate exhibit size, aspect ratio, and density of 30 nm, 10, and 2.8×10 cm, respectively. These high-aspect-ratio Si nano-pillar array helps to enhance the Fowler-Nordheim tunneling based carrier injection and to facilitate the complete relaxation on total internal reflection, thus increasing the quantum efficiency by one order of magnitude and improving the light extraction from the nano-roughened device surface by three times at least. The light-emission intensity, turn-on current and power-current slope of the MOSLED are 0.2 mW/cm, 20-30 A and 30.5 mW/A, respectively. At a biased current of 400 A, the highest external quantum efficiency is over 0.2% to obtain the maximum EL power of >1 W. In compared with the same device made on smooth Si substrate under a power conversion ratio of 1×10, such a output power performance is enhanced by at least one order-of-magnitude. Introduction: This project proposes to study the structural and physical aspects and the specific fabrication techniques in developing versatile Si nano structures, including nanocrystallite Si dot/rod/pillar/pyramid, and nano-Si/metal co-doped mesoporous silica, and self-aggregated noble metal on Si-rich Silica. These novel material systems will be soon applied to different researching fields for comprehensive studies in electronics, photonics and nio-photonics. Three featured subjects are investigated. First of all, a preliminary investigation on the characteristics of high-aspect Si nano-pillar array with a rod size in the quantum confinement regime will be demonstrated, including the photoluminescence, electroluminescence, linear and nonlinear optical coefficiences at visible and near-infrared wavelengths. Such a long Si nano-pillar will be fabricated and geometrically Report Documentation Page Form Approved