Surface Termination Control in Chemically Deposited PbS Films: Nucleation and Growth on GaAs(111)A and GaAs(111)B

Abstract

This study addresses the question of whether chemically deposited PbS thin films grown on GaAs(111) are affected by the oppositely terminated substrate surfaces, gallium terminated GaAs(111)A and arsenic terminated GaAs(111)B. The differences in PbS film deposition pathway in both cases of substrate surface termination were investigated using X-ray photoelectron spectroscopy (XPS), Raman scattering, and contact potential difference (CPD) measurements. The morphology, microstructure, and crystallographic orientation of the films were studied using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. XPS and CPD measurements indicated that PbS films deposited on oppositely terminated GaAs(111) surfaces possessed corresponding surface terminations, with PbS(111)B obtained on GaAs-(111)B and PbS(111)A on GaAs(111)A. Subsequently, different surface oxides were detected by XPS on A and B terminated PbS(111), with lead oxide obtained on PbS(111)A and PbSO 3 obtained on PbS(111)B. Moreover, CPD measurements revealed that PbS(111)A shows a 40 mV smaller work function than PbS(111)B surfaces, therefore emphasizing the importance of polarity and surface termination control for heterojunction based electronic devices.

Size Selected Clusters on Surfaces

“…Both the peak transitions of Pb(4f 7/2 ) centered at 137.4 eV and S(2p) centered at 160.6 eV indicated the unoxidized nature of the deposited lead sulfide clusters. [26] A further quantitative analysis of XPS results revealed that the ratio of Pb to S was found to be about 1:1, which doubly confirmed the deposition of PbS clusters. Given the presence of size-defined (PbS) 32 clusters on the surface as the starting point, we were assured that the observed STM images were the result of two-dimensional nucleation between (PbS) 32 clusters and/or between nano-blocks composed of multiple (PbS) 32 units.…”

(PbS)32: A baby crystal

“…17 The absence of any spectral intensity in the S(2p) region above 164 eV indicates that there is no sulfur oxidation. This data is shown in Figure 6.…”

Hetero-Twinning in Chemical Epitaxy of PbS Thin Films on GaAs Substrates

“…12 It is reasonable to assume that during nucleation, transformations with smallest atomic displacements and lattice strains are normally favored with respect transformations which involve greater changes. Furthermore, comparison of the radii of Ga in GaAs and Pb in PbS, point out very close proximity (ca.…”