Time of Flight Low Energy Atom Scattering Spectroscopy
Pascal Co., Ltd
Surface Structure and Elemental Analysis of Thin Films, Ultra Thin Films, Monolayer Films, Graphene and etc., for Insulators, Semiconductors and Metals.
⋆ Atom scattering spectroscopy,– TOFLAS, is sensitive to the top most several layers of crystal surface.
⋆ TOFLAS Pole-figures make it easy to find surface polarity, crystal orientation and the crystallographic symmetry.
⋆ Free From Electric and/or Magnetic Field.
The low energy ion scattering spectroscopy (LEIS) is a powerful method for surface crystal structure and elemental composition analysis of the topmost several layers of the crystal surface. However, analyses of insulator surface have been very difficult because of the electric charge-up caused by positive ions. To overcome the difficulties of charge up effects on insulator surfaces, we have developed a new type of surface instrument, – TOFLAS-3000 (Time Of Flight Low energy Atom Scattering spectroscopy).
TOFLAS-3000 is composed of ionization source, neutralization room (converting ions to atoms), micro-channel plate (MCP) detector and main analysis vacuum chamber.
The ions generated in the ionization source are accelerated and chopped into a pulsed beam. The pulsed beam is neutralized in the neutralization room and transformed into neutral (atom) beam.
The atom beam hitting the sample surface is scattered all the directions. Only backward-scattered atoms are detected by MCP detector, the energy and frequency of detected atoms are measured by time of flight (TOF) analysis.
Element and structural analysis of a crystal surface can be made by the time of flight techniques, because energy and frequency of scattered atoms depend on the mass and the density of the target atom in/on the crystal surface.
When the atoms in the second and the third atomic layers are covered by the shadow corn of the first atomic layer as shown in the left (A), the atoms only in the first atomic layer can be detected.
In case of (B), te first and the second layer's atoms are detected. Thus, the crystal structure of the crystal surface can be analyzed by examining the incident angle dependence of the scattered intensity at desired flight time.
The ion beam is neutralized by the charge-exchange reaction by the light collision with surrounding neutral gas atoms when ion beam passes through a neutralizer.
Atom beams make it possible to reveal insulator surface Structures
1. Surface analysis for not only metal/semiconductors but also insulators.
2. In-situ analysis in a strong electric/magnetic fields is also possible.
3. Possible to analyze the sample with electrically floating condition.
1. Structure analysis of surface layers
2. Pole figure analysis of a polar surface
3. Single-atomic-layer growth monitir
4. Analysis of surface segregation
5. Criteria of crystal growth modes
6. In-situ analysis in electric/magnetic fields
|Probe particles||Probe atoms||He, Ne, Ar|
|Beam size||Ф2mm (possible to change)|
|Neutralization chamber||Neutralization gas||He, Ne, Ar (same with probe gas)|
|Neutralization efficiency||50% (He) or more|
|Atomic beam intensity monitoring function||Option|
|Scattered particle detection||Microchannel plate||MCP: 3 steps, Effective diameter: 20|
|Detected solid angle||0.05str|
|Resolution||Time of flight resolution||10nsec|
|Atomic beam pulse width||50-100nsec|
|Vacuum||Analysis chamber arrival pressure||~10-6Pa or better|
|Analysis room exhaust system||Turbo molecular pump, Scroll pump, Titanium getter pump (standard)|
|Sample driving system||XYZ horizontal moving||Manual (X:+-5mm; Y:+-5mm, Z:+-10mm)|
|Polar angle, azimuth rotation||PC control (Polar angel:+-90; Azimuth angle: +-180)|
|Measurement system||Single TOF spectrum measurement||Full scale range (1~100.000count)|
|Step pulse standby time: 10~50µsec|
|Single spectrum measurement time (standard)||20sec or less|
|Polar angle scan range||-90 ~ +90 / Minimum angle step: 0.1|
|Azimuth angle scan range||-180 ~ +180 / Minimum angle step: 0.1|
|Scan monitor||In-situ monitoring of signal strength per angle|
|Omnidirectional scan (pole figure)||Mode: 10x10, 50x50, 100x100, 200x200|
|Time change measurement||Timer Routine mode, Continuous mode|
|Dimensions / Weight||Body: W1.660mm x H1.655mm x D750mm|
|Main chamber: Ф300mm|
|Power supply||AC100V, 20A, 50/60Hz|
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