A note on surface states of the (0001) graphite surface

1985 ◽  
Vol 35 (4) ◽  
pp. 469-472 ◽  
Author(s):  
M. Tomášek ◽  
Š. Pick
Keyword(s):  
Surface States ◽  
Graphite Surface

Zero-loss omega-filtered REM and RHEED on the new Zeiss 912

1991 ◽  
Vol 49 ◽  
pp. 616-617
Author(s):  
J.C.H. Spence ◽  
J. Mayer
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Surface States ◽  
Ccd Camera ◽  
Dark Field ◽  
Ion Pump ◽  
Magnetic Imaging ◽  
Reflection Electron Microscopy ◽  
Diffraction Patterns ◽  
Large Background

The Zeiss 912 is a new fully digital, side-entry, 120 Kv TEM/STEM instrument for materials science, fitted with an omega magnetic imaging energy filter. Pumping is by turbopump and ion pump. The magnetic imaging filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. The energy loss intensity distribution may also be displayed on the screen, and recorded by scanning it over the PMT supplied. If a CCD camera is fitted and suitable new software developed, “parallel ELS” recording results. For large fields of view, filtered images can be recorded much more efficiently than by Scanning Reflection Electron Microscopy, and the large background of inelastic scattering removed. We have therefore evaluated the 912 for REM and RHEED applications. Causes of streaking and resonance in RHEED patterns are being studied, and a more quantitative analysis of CBRED patterns may be possible. Dark field band-gap REM imaging of surface states may also be possible.

Study of Tip-Surface Interactions in Scanning Tunneling Microscopy (STM) by Reflection Electron Microscopy (REM)

1990 ◽  
Vol 48 (1) ◽  
pp. 320-321
Author(s):  
W. Lo ◽  
J.C.H. Spence ◽  
M. Kuwabara
Keyword(s):  
High Resolution ◽  
Elastic Strain ◽  
Tunneling Current ◽  
Surface Damage ◽  
Surface Interactions ◽  
Graphite Surface ◽  
Scanning Tunneling ◽  
Large Area ◽  
Tunneling Microscopy ◽  
High Resolution Tem

Work on the integration of STM with REM has demonstrated the usefulness of this combination. The STM has been designed to replace the side entry holder of a commercial Philips 400T TEM. It allows simultaneous REM imaging of the tip/sample region of the STM (see fig. 1). The REM technique offers nigh sensitivity to strain (<10−4) through diffraction contrast and high resolution (<lnm) along the unforeshortened direction. It is an ideal technique to use for studying tip/surface interactions in STM.The elastic strain associated with tunnelling was first imaged on cleaved, highly doped (S doped, 5 × 1018cm-3) InP(110). The tip and surface damage observed provided strong evidence that the strain was caused by tip/surface contact, most likely through an insulating adsorbate layer. This is consistent with the picture that tunnelling in air, liquid or ordinary vacuum (such as in a TEM) occurs through a layer of contamination. The tip, under servo control, must compress the insulating contamination layer in order to get close enough to the sample to tunnel. The contaminant thereby transmits the stress to the sample. Elastic strain while tunnelling from graphite has been detected by others, but never directly imaged before. Recent results using the STM/REM combination has yielded the first direct evidence of strain while tunnelling from graphite. Figure 2 shows a graphite surface elastically strained by the STM tip while tunnelling (It=3nA, Vtip=−20mV). Video images of other graphite surfaces show a reversible strain feature following the tip as it is scanned. The elastic strain field is sometimes seen to extend hundreds of nanometers from the tip. Also commonly observed while tunnelling from graphite is an increase in the RHEED intensity of the scanned region (see fig.3). Debris is seen on the tip and along the left edges of the brightened scan region of figure 4, suggesting that tip abrasion of the surface has occurred. High resolution TEM images of other tips show what appear to be attached graphite flakes. The removal of contamination, possibly along with the top few layers of graphite, seems a likely explanation for the observed increase in RHEED reflectivity. These results are not inconsistent with the “sliding planes” model of tunnelling on graphite“. Here, it was proposed that the force due to the tunnelling probe acts over a large area, causing shear of the graphite planes when the tip is scanned. The tunneling current is then modulated as the planes of graphite slide in and out of registry. The possiblity of true vacuum tunnelling from the cleaned graphite surface has not been ruled out. STM work function measurements are needed to test this.

Thermal Laser Stimulation Technique for AlGaN/GaN HEMT Technologies Improvement

2013 ◽  
Author(s):  
Dominique Carisetti ◽  
Nicolas Sarazin ◽  
Nathalie Labat ◽  
Nathalie Malbert ◽  
Arnaud Curutchet ◽  
...  
Keyword(s):  
Surface States ◽  
Leakage Currents ◽  
Laser Stimulation ◽  
Long Term Stability ◽  
Field Plate ◽  
Gan Hemt ◽  
Die Surface ◽  
Scan Speed ◽  
Stimulation Technique

Abstract To improve the long-term stability of AlGaN/GaN HEMTs, the reduction of gate and drain leakage currents and electrical anomalies at pinch-off is required. As electron transport in these devices is both coupled with traps or surface states interactions and with polarization effects, the identification and localization of the preeminent leakage path is still challenging. This paper demonstrates that thermal laser stimulation (TLS) analysis (OBIRCh, TIVA, XIVA) performed on the die surface are efficient to localize leakage paths in GaN based HEMTs. The first part details specific parameters, such as laser scan speed, scan direction, wavelength, and laser power applied for leakage gate current paths identification. It compares results obtained with Visible_NIR electroluminescence analysis with the ones obtained by the TLS techniques on GaN HEMT structures. The second part describes some failure analysis case studies of AlGaN/GaN HEMT with field plate structure which were successful, thanks to the OBIRCh technique.

Influence of Surface States on Gas Response Properties of Pt/TiO2

2012 ◽  
Vol 27 (9) ◽  
pp. 928-932
Author(s):  
Mao-Lin ZHANG ◽  
Zhan-Heng YUAN ◽  
Jian-Ping SONG ◽  
Cheng ZHENG
Keyword(s):  
Surface States ◽  
Response Properties ◽  
Gas Response

Softsensorgestützte Oberflächenkonditionierung beim Außenlängsdrehen 42CrMo4/Development of a reference force model for soft sensor supported surface conditioning during longitudinal turning of AISI 4140 QT

2020 ◽  
Vol 110 (11-12) ◽  
pp. 758-762
Author(s):  
Daniel Gauder ◽  
Michael Biehler ◽  
Benedict Stampfer ◽  
Benjamin Häfner ◽  
Volker Schulze ◽  
...  
Keyword(s):  
White Layer ◽  
Surface States ◽  
Soft Sensor ◽  
Sensor Technology ◽  
Force Model ◽  
Destructive Testing ◽  
Surface Conditioning ◽  
Testing Technology ◽  
Process Detection ◽  
Longitudinal Turning

Das Forschungsprojekt „Prozessintegrierte Softsensorik zur Oberflächenkonditionierung beim Außenlängsdrehen von 42CrMo4“ widmet sich der Entstehung und der In-process-Erfassung von industriell relevanten Randschichtzuständen. Im Speziellen werden sogenannte White Layer und Eigenspannungszustände untersucht. Durch die modulare Verknüpfung von zerstörungsfreier Prüftechnik, Simulationsergebnissen und Prozesswissen mittels Datenfusion wird ein Softsensor erforscht. Dieser soll im Rahmen einer adaptiven Regelung des Drehprozesses eingesetzt werden und eine gezielte Einstellung von vorteilhaften Randschichtzuständen erlauben. The research project „Process-integrated soft sensor technology for surface conditioning during external longitudinal turning of 42CrMo4“ is dedicated to the formation and in-process-detection of surface layers with industrial relevance. In particular, so-called white layers and residual stresses are investigated. A soft sensor is being researched through the modular combination of non-destructive testing technology and process knowledge by means of data fusion. This is to be used in the context of an adaptive control of the turning process in order to adjust beneficial surface states.

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