3,117 research outputs found
Scanning Tunneling Microscopy and Tunneling Luminescence of the Surface of GaN Films Grown by Vapor Phase Epitaxy
We report scanning tunneling microscopy (STM) images of surfaces of GaN films
and the observation of luminescence from those films induced by highly
spatially localized injection of electrons or holes using STM. This combination
of scanning tunneling luminescence (STL) with STM for GaN surfaces and the
ability to observe both morphology and luminescence in GaN is the first step to
investigate possible correlations between surface morphology and optical
properties.Comment: 12 pages, Revtex 3.0, submitted to Appl. Phys. Lett., three figures
available from Jian Ma at [email protected]
Ge quantum dot arrays grown by ultrahigh vacuum molecular beam epitaxy on the Si(001) surface: nucleation, morphology and CMOS compatibility
Issues of morphology, nucleation and growth of Ge cluster arrays deposited by
ultrahigh vacuum molecular beam epitaxy on the Si(001) surface are considered.
Difference in nucleation of quantum dots during Ge deposition at low (<600 deg
C) and high (>600 deg. C) temperatures is studied by high resolution scanning
tunneling microscopy. The atomic models of growth of both species of Ge
huts---pyramids and wedges---are proposed. The growth cycle of Ge QD arrays at
low temperatures is explored. A problem of lowering of the array formation
temperature is discussed with the focus on CMOS compatibility of the entire
process; a special attention is paid upon approaches to reduction of treatment
temperature during the Si(001) surface pre-growth cleaning, which is at once a
key and the highest-temperature phase of the Ge/Si(001) quantum dot dense array
formation process. The temperature of the Si clean surface preparation, the
final high-temperature step of which is, as a rule, carried out directly in the
MBE chamber just before the structure deposition, determines the compatibility
of formation process of Ge-QD-array based devices with the CMOS manufacturing
cycle. Silicon surface hydrogenation at the final stage of its wet chemical
etching during the preliminary cleaning is proposed as a possible way of
efficient reduction of the Si wafer pre-growth annealing temperature.Comment: 30 pages, 11 figure
Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular Beam Epitaxy Grown Monolayer Vanadium Ditelluride.
We present a combined experimental and theoretical study of monolayer vanadium ditelluride, VTe2, grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using various in situ microscopic and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, together with theoretical analysis by density functional theory calculations, we demonstrate direct evidence of the metallic 1T phase and 3d1 electronic configuration in monolayer VTe2 that also features a (4 Ă 4) charge density wave order at low temperatures. In contrast to previous theoretical predictions, our element-specific characterization by X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to the monolayer. Our findings provide essential knowledge necessary for understanding this interesting yet less explored metallic monolayer in the emerging family of van der Waals magnets
Correction to Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular-Beam Epitaxy Grown Monolayer Vanadium Ditelluride.
It has been brought to our attention that a mistake exists in the author list. The author âJohnson Gohâ in the original article should be âKuan Eng Johnson Gohâ. His primary corresponding email is [email protected]
Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 {\deg}C
The article presents an experimental study of an issue of whether the
formation of arrays of Ge quantum dots on the Si(001) surface is an equilibrium
process or it is kinetically controlled. We deposited Ge on Si(001) at the room
temperature and explored crystallization of the disordered Ge film as a result
of annealing at 600 {\deg}C. The experiment has demonstrated that the
Ge/Si(001) film formed in the conditions of an isolated system consists of the
standard patched wetting layer and large droplike clusters of Ge rather than of
huts or domes which appear when a film is grown in a flux of Ge atoms arriving
on its surface. We conclude that the growth of the pyramids appearing at
temperatures greater than 600 {\deg}C is controlled by kinetics rather than
thermodynamic equilibrium whereas the wetting layer is an equilibrium
structure.Comment: Accepted for publication in Nanoscale Research Letter
- âŠ