Ambient-pressure Photoemission Spectroscopy Systems
(대기압 광전자 방출 측정 시스템)
Description | ||||||||
---|---|---|---|---|---|---|---|---|
The Ambient-pressure Photoemission Spectroscopy (APS) systems are one of KP Technology Ltd’s most recent additions to our large surface analysis range. Domestic and international patents are held for these instruments. APS measures the absolute work function (Φ) of a material by photoemission in ambient conditions, no vacuum is required. The excitation range of APS is 3.4 eV to over 7.0 eV, meaning that APS is capable of measuring the absolute work function of metals and the ionization potential of semiconductors alongside measurement of the surface Fermi level with the Kelvin probe.
|
||||||||
Features | Applications | |||||||
• Work function measurement by photoemission in air | • Organic and non-organic semiconductors | |||||||
• Density of states measurements | • Metals and metal alloys | |||||||
• 3.4 eV to 7.0 eV energy range | • Thin Films and surface oxides | |||||||
• Measurement of all semiconductor bands | • Corrosion and nanotechnology | |||||||
• Contact potential difference by Kelvin probe | • Solar cells and organic photovoltaics | |||||||
Measurement Principle | ||||||||
When light is incident on a material such as a metal or a semiconductor, the photons may have enough energy to liberate electrons from the surface, a process known as the Photoelectric Effect.
The energy required for electrons to escape the material is termed the work function. By varying the energy of the incoming light, the absolute work function can be established.
|
||||||||
Each metal was measured with the photoemission mode and Kelvin probe mode of an APS02 system. The contact potential difference (CPD) was measured with the Kelvin probe and the work function was measured by the ambient pressure photoemission mode. When work function is plotted against CPD, a straight line is formed. A line is drawn at 0 V CPD to the line and when traced down reveals the absolute work function of the tip. | ||||||||
Density of States | ||||||||
The properties of many materials are governed by the Density of States (DOS) near the Fermi level. The Ambient-pressure Photoemission system is capable of probing the DOS by differentiating the detected photoelectron yield with respect to the incident photon energy. The DOS measurement can thus be compared to molecular orbital calculations for the material under investigation. DOS data collected with the APS in air is shown to the right for copper. The data for all measured samples is consistent with literature. | ||||||||
System Overview | ||||||||
System Specifications | APS01 | APS02 | APS03 | APS04 | ||||
Kelvin probe 3-axis scanning | V | V | V | |||||
Surface Photovoltage | V | V | ||||||
Surface Photovoltage Spectroscopy | V | |||||||
Tip material / diameter | 2 mm gold tip | |||||||
CPD resolution | 1-3 meV | |||||||
Height control (Auto) | 25 mm automatic | |||||||
Kelvin probe mode and PE mode | CPD and photoemission measurements | |||||||
CPD measurement time | CPD measurements in | |||||||
PE resolution | Full photoemission measurement | |||||||
WF measurement time | PE measurement in | |||||||
DOS measurements | Full access to DOS information | |||||||
Optical system | Colour camera with zoom lens and monitor for positioning | |||||||
Oscilloscope | Digital TFT oscilloscope for real-time signal | |||||||
Test sample | Gold, aluminum and silver test samples | |||||||
Faraday enclosure base | 450 x 450 mm | |||||||