Time evolution of Nano Dots created on InP(111) surfaces by keV irradiation

Abstract

AbstractFabrication of Nanodots on semiconductor surfaces has immense importance due to their application in memory and optoelectronic devices. Ion irradiation methods display an easy and cost effective route for developing self assembled structures. We have studied the formation of Nano-dots on InP(111) surfaces by 3keV Ar ion irradiation. The distribution of nano Dots on InP surfaces has been investigated by Scanning Probe Microscopy (SPM). A 5 min irradiation of InP surface with Ar ions leads to the appearance of dots on the surface. The density of dots is, however very small. These dots have been obtained at room temperature, in the absence of sample rotation, with an angle of 15 degree between the ion axis and the sample normal. After an irradiation of 10 min a large density of dots appear on InP surface and display a narrow distribution of size and height. The dots at this stage have an average diameter of 25nm and a height of 4nm. With increased irradiation time the average size and the height of the dots increase and their distribution also become broader. This scenario, however, changes after a 40 min irradiation where large rectangular shaped dots of about 100 nm diameters and 40 nm height are observed. Surprisingly, for larger irradiation times a reduction in the size and heights is observed. The studies suggest “Critical Time” tc at t= 40 min such that the dot structures grow with time below tc but diminish in size beyond it.