A versatile Kelvin probe for dynamic work function change measurements during gas adsorption and in situ film growth experiments

1997 ◽  
Vol 68 (10) ◽  
pp. 3866-3871 ◽  
Author(s):  
M. Schmidt ◽  
M. Nohlen ◽  
G. Bermes ◽  
M. Böhmer ◽  
K. Wandelt
Keyword(s):  
Work Function ◽  
Gas Adsorption ◽  
Film Growth ◽  
Kelvin Probe ◽  
Dynamic Work ◽  
Function Change ◽  
Work Function Change ◽  
Growth Experiments

Very Low Pressure Oxidation of Si and Ge Surfaces

1990 ◽  
Vol 204 ◽  
Author(s):  
Iain D. Baikie
Keyword(s):  
Work Function ◽  
Substantial Reduction ◽  
Second Phase ◽  
Kelvin Probe ◽  
Band Bending ◽  
Effective Electron ◽  
Adsorption Phase ◽  
Dipole Layer ◽  
Function Change ◽  
Work Function Change

ABSTRACTAlthough the oxidation of Si(111) 7×7, Ge(111) 2×8 surfaces are relatively well understood very little work has been performed at sub monolayer coverage. We have utillsed a custom-built high resolution Kelvin probe to follow the changes in work function, and changes in band-bending and surface state occupancy via Surface Photovoltage Spectroscopy (SPV). The Kelvin probe Is an Ideal tool for such analysis due to Its extremely high surface sensitivity, equivalent to 4×1010 molecules/cm2, or 0.01% of the available sites.We observe a very rapid initial adsorption phase, which has not been found by other surface probes, e.g., AES, EELS, etc, corresponding to the formation of an elementary dipole layer. During this phase the Increase In the effective electron affinity with oxygen uptake achieves a maximum of 1V at 0.3 monolayer (ML), on SI(111) at 300 K. We report, for the first time, SPV spectra of SI(111), at 100 K, indicating quenching of a band of surface states centered around the fermi-level, quenching Is completed at the max-Imum of the work function change.The second adsorption phase, involving oxygen penetration through the surface layer and incorporation Into the lattice, commences at 0.25 ML for Si(111) at 300 K. a much earlier stage than previously reported. Further. we find evidence of a metastable SiO2 precursor at coverages below 1 ML. The dipole layer formation (and breakup) is shown to be very sensitive to both temperature and amount of surface Carbon contamination. The second phase also Involves a substantial reduction In band-bending to nearly flat bands at 2 ML, accounting for 20% of the work function change In the case of SI and almost 90% for Ge.

Work Function Study for the Search of Efficient Target Materials for Use in Hyperthermal Surface Ionization Using a Scanning Kelvin Probe

2000 ◽  
Vol 623 ◽  
Author(s):  
U. Petermann ◽  
I.D. Baikie ◽  
B. Lägel ◽  
K.M. Dirscherl
Keyword(s):  
Work Function ◽  
Surface Ionization ◽  
Kelvin Probe ◽  
Scanning Kelvin Probe ◽  
Flash Annealing ◽  
Function Change ◽  
Work Function Change ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Ongoing Project

AbstractIn order to search for efficient target materials for use in Hyperthermal Surface lonisation (HSI), a new mass spectroscopy ionisation technique, we have performed a study of high and low work function (ø) surfaces as part of an ongoing project. HSI relies on high and low work function surfaces for the production of positive (pHSI) and negative (nHSI) ions, respectively.Using a novel UHV Scanning Kelvin Probe we have followed the oxidation kinetics of polycrystalline Re at different temperatures and examined the effects of oxidation, flash annealing and sputter-anneal cleaning cycles via high resolution work function topographies. Our results indicate that oxidised Re is the best candidate for pHSI in terms of ionisation efficiency and ø change. The peak work function change of 2.05 eV occurred at 900 K to 950K.For the nHSI materials Calcium exhibited the best performance with respect to the ionisation efficiency indicating a wf of 2.9 eV. We will present data in terms of mass fragmentation using an HSI-Time-of-Flight (TOF) system and time stability of the work function.

GROWTH INVESTIGATIONS OF ULTRATHIN Ag FILMS ON Pt(111) USING STM AND DYNAMICAL WORK FUNCTION MEASUREMENTS

1997 ◽  
Vol 04 (06) ◽  
pp. 1179-1183 ◽  
Author(s):  
S. GESTERMANN ◽  
M. NOHLEN ◽  
M. SCHMIDT ◽  
K. WANDELT
Keyword(s):  
Work Function ◽  
The Other ◽  
Initial Growth ◽  
Function Change ◽  
Work Function Change

The growth of Ag on Pt(111) has been studied with in situ work function change measurements and STM at deposition temperatures of 350 K and 520 K. The strain of the compressively stressed Ag monolayer is relieved in the submonolayer regime by the development of two different reconstructions. One of these reconstructions occurs only at higher coverages (Θ<0.85 ML), partially displacing the other reconstruction which is found on all submonolayer Ag films. For coverages beyond one monolayer the first monolayer Ag becomes pseudomorphic with the Pt(111) substrate. Based on a different work function behavior for a deposition at 350 K and 520 K, respectively, we suggest different mechanisms for the disappearance of these reconstructions during the completion of the first Ag layer and the initial growth of the second layer.

Work function studies of propylene, acetylene, hydrogen and nitrogen chemisorption on molybdenum

1982 ◽  
Vol 47 (11) ◽  
pp. 2996-3003
Author(s):  
Zdeněk Bastl
Keyword(s):  
Work Function ◽  
Surface Topography ◽  
Surface Coverage ◽  
Dissociative Chemisorption ◽  
Complete Coverage ◽  
Surface Sites ◽  
Function Change ◽  
Work Function Change

The work function changes of vacuum deposited molybdenum films caused by the chemisorption of propylene, acetylene, hydrogen and nitrogen were measured using the Kelvin vibrating capacitor method. During the hydrocarbon chemisorption, the work function increased in a low surface coverage region but decreased at the higher surface coverages. The saturation values of the work function changes corresponding to complete coverage of the surface by chemisorbed propylene and acetylene equal -0.08 eV and -0.42 eV, respectively. The observed dependences of the work function change on surface coverage are interpreted by the dissociative chemisorption of hydrocarbons on a limited number of surface sites which are simultaneously the sites of preferred adsorption. The extent of dissociation decreases in the adsorption with the increasing surface coverage. The results of the study of the work function changes induced by the hydrogen and nitrogen chemisorption enabled to draw several conclusions on the surface topography of the used films.

Fundamental studies on SnO2 by means of simultaneous work function change and conduction measurements

2005 ◽  
Vol 490 (1) ◽  
pp. 43-47 ◽  
Author(s):  
T. Sahm ◽  
A. Gurlo ◽  
N. Bârsan ◽  
U. Weimar ◽  
L. Mädler
Keyword(s):  
Work Function ◽  
Function Change ◽  
Work Function Change

In situ work function study of oxidation and thin film growth on clean surfaces

1999 ◽  
Vol 433-435 ◽  
pp. 770-774 ◽  
Author(s):  
I.D Baikie ◽  
U Petermann ◽  
B Lägel
Keyword(s):  
Thin Film ◽  
Work Function ◽  
Film Growth ◽  
Thin Film Growth ◽  
Function Study
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