FORMATION OF SILICON NANOCRYSTALS IN SiO2 BY SILICON IMPLANTATION AND SUBSEQUENT ANNEALING

Abstract

<p>Since the first description of Si nanocrystals, research in this field has gone through raid progress and potential applications of Si nanocrystals have been established. There are several methods applicable to the fabrication of Si nanocrystals with one of the most used being ion implantation followed by thermal annealing. Two types of thermal annealing are available for use: furnace annealing (FA) for several hours, normally in an N₂ atmosphere; and rapid thermal annealing (RTA) for a short time (less than a few minutes), again in an inert atmosphere such as N₂. The formation of the nanocrystals then proceeds with decomposition, segregation, diffusion, nucleation, aggregation, growth and crystallization. This formation requires temperatures in excess of 1000^o C such that noticeable photoluminescence may be observed. This thesis explores the fabrication of Si nanocrystals using the McMaster ion implanter and subsequent RTA. The implantation conditions required to form luminescent nanocrystals are determined. For example, for an implantation energy of 10 KeV a minimum dose of 1.5 10¹⁶ ions cm^-2 is required. The relationship between luminescent intensity and post-implantation annealing is also explored. An optimum annealing temperature of 1100^oC is found. For the first time to the author’s knowledge, a study of the effects of thin film thickness on luminescent intensity is conducted. The major conclusions of this thesis are i) a specific thickness of oxide layer has the maximum PL for a fixed implantation energy and implantation dose, ii) PL intensity is inversely proportional with measuring temperature., iii) the type of oxidation process has a large effect on PL intensity.</p>