Nanoscale Mapping of Strain and Composition in Quantum Dots Using Kelvin Probe Force Microscopy

Abstract

A key factor in improving quantum dots electrical properties and dots-based devices is the ability to control the crucial parameters of composition, doping, size, and strain distribution of the dots. We show that nanometer-scale work function measurements using ultrahigh vacuum Kelvin probe force microscopy is capable of measuring the strain and composition variations within and around individual QDs. This is accomplished by analyzing the detailed surface potential profiles in and around InSb/GaAs dots.

Narrow gap nano-dots growth by droplets heteroepitaxial mode

“…At the first stage of the dots formation, GaInAs crystallized on the liquid-substrate interface and clear appearance of strained regions and dislocations close to dot-substrate interface [21,29,30]. In this growth process the Indium was found at the top of the large drops, also In-reached InGaAs can be found at the bottom of the dots (Fig.…”

“…At present very little is known about the atomistic mechanism of QDs formation [20][21][22] process as a first step towards the controlled growth of DHE QDs. The DHE method consists two basic stages: the formation of low melting point element nano-droplets on the substrate, and subsequently the exposure of these droplets to the gas phase flow of one or more group IV, V or VI elements.…”

“…The factors governing the DHE nano-dots properties were studied by our group using several methods, while comparing the effects of growth conditions, substrate lattice mismatch and substrate chemical composition [11,21,29,30]. These methods which include the Peak Pairs Algorithm (PPA) [29], Kelvin Probe Force Microscopy (KPFM) [21,29] and the new X-ray diffraction Coherent Bragg Rod Analysis method (COBRA) [30], made it possible to obtain information about the local variations in the substrate-nano-dots system with sub-nano resolution, and to map the strain and composition distribution in grown structures as well as to understand the growth dynamics.…”

“…These methods which include the Peak Pairs Algorithm (PPA) [29], Kelvin Probe Force Microscopy (KPFM) [21,29] and the new X-ray diffraction Coherent Bragg Rod Analysis method (COBRA) [30], made it possible to obtain information about the local variations in the substrate-nano-dots system with sub-nano resolution, and to map the strain and composition distribution in grown structures as well as to understand the growth dynamics. The results indicate that the DHE mode is a promising flexible technique for growing InSb and InAsSb nanoscale structures on different substrates.…”

Kelvin Probe Force Microscopy in Nanoscience and Nanotechnology

“…Topographic and CPD images of $40 nm InSb nanodots grown on GaAs substrates were measured [27]. Though an obvious correlation between the two images is observed, the dark rings around the dots observed in the CPD image and the CPD peak heights do not match the work function difference between InSb and GaAs, indicating the composition changes.…”