Xavier / X-TRONIX LTD
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The Kelvin Probe Principles
When two conducting materials with different work functions are brought together, for example via an external wire contact, electrons in the material with the lower work function flow to the one with the higher work function. If these materials are made into a parallel plate capacitor, equal and opposite surface charges form. Measuring the contact potential is then exquisitely simple: an external potential is applied to the capacitor until the surface charges disappear, and at this point the external potential equals the contact potential. Kelvin realized this experimentally measured using two large flat polished disc's of Zinc ...
<< MORE >>In situ work function study of oxidation and thin film growth on clean surfaces
Authors: I.D.
Baikie, U. Petermann, B. Lägel
Abstract: Using a novel ultra high vacuum compatible Kelvin probe a study is made of the work function (
f) changes on semiconductors and metals occurring during basic surface processing, for example, surface cleaning, sputtering, oxidation and thin film growth. It shows that damage of the
...
Helium atoms get the ride of their life
To the adrenaline junkie mid-way through a bungee jump, gravity must feel like it can accelerate matter at a spectacular rate. At the atomic scale, however, when it comes to shifting around neutral particles, gravity is incredibly ineffective compared with other fundamental interactions such as the strong and weak nuclear forces.
Now, however, a team of physicists in Germany has shown that a little-known interaction caused by electric fields known as the "ponderomotive" force can accelerate neutral particles at up to 1014 ... << MORE >>
About Static and Dynamic SIMS
In static SIMS, dedicated to the analysis of the top monolayer, the primary ion dose is kept below 112 ions/cm2 and the mass spectrum reveals MOLECULAR information. In dynamic SIMS mode, the primary ion dose is not limited and exceeds 112 ions/cm2. In this mode, ELEMENTAL and ISOTOPIC information can be obtained from the mass spectrum. It allows surface, "bulk" and 2D/3D analysis.
The ionization yield of most elements varies by decades, depending on the chemical ...<< MORE >>
Is dark matter mostly 'dark atoms'?
Sep 21, 2009 - www.PhysicsWorld.com
Physicists currently believe that most of the dark matter in the universe is made up of individual particles, and the challenge is to work out what kind of particles these are. New research, however, overturns this assumption and says that observational and experimental data are better explained if dark matter exists as composite particles – atoms of dark protons and dark electrons that are acted on by the dark-matter equivalent of the electromagnetic force.
Dark matter is thought to make up more than 80% of the ...<< MORE >>
The Extent Of Our Universe In Time & Space
(Music: Wagner's Lohengrin Prelude)
Part 1
Part 2
...<< MORE >>
Inhomogeneity of a highly efficient InGaN based blue LED studied by 3D atom probe tomography
The InGaN based multiple quantum well (MQW) structure in a commercially available white light emitting diode (LED) was studied by transmission electron microscopy (TEM) and three-dimensional atom probe tomography (APT). The average In mole fraction by three-dimensional (3D) APT was found to be about 18% in the InGaN well which is consistent with the secondary ion mass spectrometry (SIMS) analysis.
The In distribution in the InGaN well layer was analyzed by the iso curve mapping of 3D APT and found to be nonuniform in the InGaN active layer. In clustering or In rich regions in the range of ...<< MORE >>
DNA sequencing using STM
Stuart Lindsay and his collaborators use genetic material to bridge the gap between a scanning tunnelling microscope and a sample of interest.
As the tip scans along the surface, the genetic material either bonds or ignores the underlying genetic material - leading to a varying tunnelling current. The resulting image reveals the identity of the DNA sample under inspection.
Quantum physics could come to the aid of medical science as a new technique for identifying DNA utilizes the quantum effect of tunnelling. The method, developed by physicists in the US, will enable users to read genetic codes directly by studying DNA with ...<< MORE >>
Tips & Tricks - Vacuum Viewports
This had already been posted back in September 2007 and as it did attract tremendous interest I'm happy to give it a makeover with more detail !
For those who do not often change things on a UHV vacuum system, here's some tips if you need to mount a viewport. First, never use a viewport that appears to be, or is known to be damaged. A replacement viewport costs far less than repairing a system that has been subject of an implosion caused by a faulty viewport.
SAFETY
Pressure differentials: Kodial VPZ viewports are designed to withstand 1 Bar differential pressure. Other standard ...<< MORE >>