Work function study of rhenium oxidation using an ultra high vacuum scanning Kelvin probe

2000 ◽  
Vol 88 (7) ◽  
pp. 4371 ◽  
Author(s):  
I. D. Baikie ◽  
U. Petermann ◽  
A. Speakman ◽  
B. Lägel ◽  
K. M. Dirscherl ◽  
...  
Keyword(s):  
Work Function ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Kelvin Probe ◽  
Function Study ◽  
Scanning Kelvin Probe

Characterization of Oxides and Thin Films

1993 ◽  
Vol 309 ◽  
Author(s):  
Iain D. Baikie ◽  
Gerrit H. Bruggink
Keyword(s):  
Work Function ◽  
Local Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Interface Condition ◽  
Semiconductor Surface ◽  
Kelvin Probe ◽  
Preparation Methods ◽  
Surface And Interface ◽  
Wide Range

AbstractUsing a new, high resolution, microscopic Scanning Kelvin Probe (SKP), work function topographies of metal, semiconductor and metal/semionductor surfaces have been studied in both Ultra-High-Vacuum (UHV) and air environments.The work function is a very sensitive indicator of surface and Interface condition and has been previously utilized to examine preparation methods, surface roughness, adsorption processes, thin film monitoring and residual surface contamination.Extension of the basic method, via Illumination of the semiconductor surface under the tip allows one to probe the local density of states (LDOS). Variations in LDOS can be used to monitor metal contamination, interface traps, bulk contamination, oxide imperfections, etc.Work function topographies generated in this fashion have application in quality control at all stages of the manufacturing process. The Kelvin method of measuring work function is non-contact and non-destructive, utilizing neither high fields nor large currents. It can be applied to a variety of environments ranging from UHV to air and at a wide range of temperatures.

A Novel Method for True Work Function Determination of Metal Surfaces by Combined Kelvin Probe and Photoelectric Effect Measurements

2000 ◽  
Vol 619 ◽  
Author(s):  
Bert Lägel ◽  
Iain D. Baikie ◽  
Konrad Dirscherl ◽  
Uwe Petermann
Keyword(s):  
Thin Film ◽  
Work Function ◽  
Metal Surfaces ◽  
Surface Condition ◽  
High Vacuum ◽  
Photoelectric Effect ◽  
Ultra High Vacuum ◽  
Kelvin Probe ◽  
Novel Method

ABSTRACTWe have developed a novel method for in-situ measurements of the true work function (ø) of metal surfaces by combined ultra-high vacuum compatible Kelvin Probe and photoelectric effect measurements. The work function is an extremely sensitive parameter of surface condition and can be used to study oxidation and thin film growth on metal surfaces. For example, the increase in ø due to oxidation of polycrystalline rhenium is 1.9eV.The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (øtip) is unknown.We present a novel approach to measure øtip with the Kelvin Probe via the photoelectric effect, using a Gd foil as the photoelectron source, hereby combining the advantages of both methods to provide the absolute work function of the sample surface. We demonstrate the application of the technique by in-situ work function measurements during oxidation of polycrystalline rhenium. The extended Kelvin Probe method therefore has potential applications as a characterisation tool for thin film epitaxy and work function engineering of surfaces.

A Novel Approach for True Work Function Determination of Electron-Emissive Materials by Combined Kelvin Probe and Photoelectric Effect Measurements

2000 ◽  
Vol 621 ◽  
Author(s):  
Bert Lägel ◽  
Iain D. Baikie ◽  
Konrad Dirscherl ◽  
Uwe Petermann
Keyword(s):  
Work Function ◽  
High Vacuum ◽  
Sample Surface ◽  
Photoelectric Effect ◽  
Ultra High Vacuum ◽  
Chemical Contamination ◽  
Kelvin Probe ◽  
Non Invasive ◽  
Novel Approach ◽  
The Stability

ABSTRACTFor the development of new electron-emissive materials knowledge of the work function Φ and changes in Φ is of particular interest. Among the various methods, the ultra-high vacuum (UHV) compatible scanning Kelvin Probe has been proven to be a superior technique to measure work function changes due to e.g. UHV cleaning processes, chemical contamination, thermal processing etc. with high accuracy (<1meV).The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (Φtip) is unknown.Here, we present a novel approach to measure Φtip with the Kelvin Probe via the photoelectric effect, where a Gd foil is used as the photoelectron source. This method thus provides the true work function of the sample surface with an accuracy of approx. 50meV. We demonstrate the application of the technique by in situ work function measurements on evaporated layers of the low work function material LaB6 on a Re substrate and follow the changes in Φ of LaB6 due to the surface adsorption of residual gas molecules. Thus, the extended Kelvin Probe method provides an excellent tool to characterise and monitor the stability of low work function surfaces.

Laser cleaning of exfoliated graphene

2012 ◽  
Vol 1455 ◽  
Author(s):  
Oliver Ochedowski ◽  
Benedict Kleine Bußmann ◽  
Marika Schleberger
Keyword(s):  
Local Heating ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ambient Conditions ◽  
Kelvin Probe ◽  
Structural Modifications ◽  
Force Microscopy ◽  
Exfoliated Graphene ◽  
Atomic Force ◽  
P Type

ABSTRACTWe have employed atomic force and Kelvin-Probe force microscopy to study graphene sheets exfoliated on TiO2 under the influence of local heating achieved by laser irradiation. Exfoliation and irradiation took place under ambient conditions, the measurements were performed in ultra high vacuum. We show that after irradiation times of 6 min, an increase of the surface potential is observed which indicates a decrease of p-type carrier concentration. We attribute this effect to the removal of adsorbates like water and oxygen. After irradiation times of 12 min our topography images reveal severe structural modifications of graphene. These resemble the nanocrystallite network which form on graphene/SiO2 but after much longer irradiation times. From our results we propose that short laser heating at moderate powers might offer a way to clean graphene without inducing unwanted structural modifications.

Work Function Study of Polycrystalline Metals using a UHV Scanning Kelvin Probe

2000 ◽  
Vol 615 ◽  
Author(s):  
U. Petermann ◽  
I.D. Baikie ◽  
B. Lägel ◽  
K.M. Dirscherl
Keyword(s):  
Work Function ◽  
Target Material ◽  
Kelvin Probe ◽  
High Work Function ◽  
Positive Ions ◽  
Polycrystalline Metals ◽  
Scanning Kelvin Probe ◽  
Flash Annealing ◽  
Different Temperatures ◽  
High Work

ABSTRACTWe have undertaken a study of high work function (φ) surfaces as part of an ongoing project searching for efficient target materials for use in Hyperthermal Surface Ionisation (HSI), a new mass spectroscopy ionisation technique. HSI relies on high work function surfaces for the production of positive ions. Polycrystalline metals as Re, W, Mo and Pt are particularly interesting materials in this respect as oxidation substantially increases their φ. We present and discuss the following experimental evidence: a) the magnitude and sign of φ changes in terms of adsorbate induced dipoles, b) the effect of molecular hydrogen exposure on the clean surface, and c) the effect of subsequent oxygen exposure.Using a novel UHV Scanning Kelvin Probe we have followed the oxidation kinetics of polycrystalline metals at different temperatures and examined the effects of oxidation, flash annealing and sputter-anneal cleaning cycles via high-resolution φ topographies. Our results indicate in particular Re as a suitable HSI target material exhibiting a φ increase of 1050 meV at 300 K increasing to 2050 meV at 900 K. Sputter-cleaned surfaces exhibit a dramatic change in the second oxidation phase.We have also examined φ changes associated with N2O and CO2 on Tungsten and Molybdenum. We observe that atomic oxygen gives similar results to O2 but has a much lower initial sticking coefficient. We report that CO2 actually lowers the φ for substrate temperatures under 650 K, the peak work function changes occurs at 850 K and is approximately 1/3 the height of the O2 or O peak.

scholarly journals Collective amplification of nearby nanoparticles in the Coulomb blockade restricted charging of a single nanoparticle

2021 ◽  
Author(s):  
Baptiste Chatelain ◽  
Ali El Barraj ◽  
Clémence Badie ◽  
Lionel Santinacci ◽  
Clemens Barth
Keyword(s):  
Coulomb Blockade ◽  
High Vacuum ◽  
Atomic Layer ◽  
Ultra High Vacuum ◽  
Kelvin Probe ◽  
Charge Detection ◽  
Research Fields ◽  
Supported Metal Nanoparticles ◽  
General Desire ◽  
Interest In Research

Abstract The characterization of charges in oxide supported metal nanoparticles (NP) is of high interest in research fields like heterogeneous catalysis and microelectronics. A general desire is to manipulate the charge of an oxide supported single NP and to characterize afterwards the charge and its interference with the insulating support but also with nearby NPs in the vicinity. By using noncontact AFM (nc-AFM) and Kelvin probe force microscopy (KPFM) in ultra-high vacuum (UHV) and at room temperature we show that a ~5 nm small AuNP can be directly charged with electrons by the AFM tip and that upon the charging, nearby AuNPs sensitively change their electrostatic potential with a large impact on the charge detection by nc-AFM and KPFM. The AuNPs are supported on a 40 nm thick insulating Al2O3 film, which is grown by atomic layer deposition (ALD) on Si(001). Due to Coulomb blockades, the NP charging appears in the form of large and discrete peaks in detuning versus bias voltage curves. Finite element method (FEM) calculations reveal that the large peaks can only be observed when the potentials of nearby insulated NPs get modified by the NP's electron charge, according to the electrostatic induction principle. In view of the number of transferred electrons, we anticipate that after the charging, the electrons are transferred from the AuNP to the NP-Al2O3 interface or into Al2O3 subsurface regions directly underneath.

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