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掃描開爾文探針系統
Kelvin Probe

【Instytut Fotonowy】光電光譜儀 光電化學

掃描開爾文探針系統

簡介

掃描開爾文探針系統允許以高精度和準確度精確測量不同半導體和導電材料的功函數。

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描述
在光電化學中,表面狀態在電荷轉移中起著重要作用。當這種情況發生時,樣品的功函數會發生變化。

掃描開爾文探針系統允許以高精度和準確度精確測量不同半導體和導電材料的功函數。

非接觸式測量涉及振盪電容器,其中一個電極是樣品,另一個是由金網製成的振盪參考電極。因此,測量值參考金的功函數 (5.1 eV)。在足夠長的積分時間內,測量的解析度可以達到0.1meV。掃描開爾文探針系統可用於各種類型的表面研究,包括:腐蝕、吸附/解吸、表面充電、催化活性等。

為方便起見,探頭配備了激光筆和數位顯微鏡。電動垂直定位系統允許參考電極在與試樣表面的相同距離上進行重複定位(精度為10um)。
* X-Y定位可以作為一個選購安裝。

該系統還配備了寬帶光導,可與數控單色儀和高壓氙弧燈相連接。波長範圍從300到1000 nm,可用於連續或脈衝的樣品照射。這種配置允許測量表面的功函數和電荷、表面光電壓光譜和其它光物理技術,光電壓解析度高於 5 mV(應用長積分時間時為 0.1 mV)。整個系統安裝在接地的法拉第籠中,以減少電氣雜訊和漫射光的影響。這種表面光電壓光譜儀是研究光催化劑、有機和無機半導體、太陽能電池和其它光活性材料和元件的重要工具。在這種掃描開爾文探針系統/表面光電壓光譜儀的幫助下,還可以即時監測半導體的光腐蝕、光解吸和光催化反應。

系統組成

該裝置包括一個安裝在帶有Z軸電動平台的堅固支架上的振盪金探針,電子控制單元和法拉第箱。

  • 樣品被放置在手動或電動的XY平台上,在任何一個方向的移動範圍為1.5厘米。
  • 探針與Z軸平台連結,可以將其移動至在距樣品所需的距離處。
  • 紅色激光指示器顯示探針在測量過程中的擺動位置。
  • 系統被法拉第箱覆蓋後,一個USB顯微鏡和一個白色LED可幫助您觀察。
  • 光通過液體波導或光纖傳送到樣品,因此消除了可能來自光源的 EM 干擾。
  • 在閒置或存放週期,易碎的金探針可被放置在一個受保護的空間內,以防止意外損壞。
  • 該系統還配備了自動樣品高度感測器。
Voltage range -5 V .. 5 V
Voltage measurement nominal resolution 0.15 mV
Measurement technology 2-channel lock-in amplifier
Sample holder translation stage X-Y, manual (default) or motorized
X-Y stage stroke 15 mm x 15 mm
Tip type Au mesh, dia. 2.5 mm
Tip Z positioning motorized Z stage
Positioning with respect to a sample light barrier
Tip Z positioning resolution 10 µm
Spectral range for wave guides 200 nm .. 2000 nm (depending on a waveguide)
Liquid waveguides selection (Lumatec)
Auxiliary sensors humidity and temperature
Internal Faraday cage illumination white LED
X-Y positioning aid laser sample placement indicator
PC connectivity USB 2.0
Size 40 x 40 x 45 cm
Weight 10 kg

DESCRIPTION

In photoelectrochemistry surface states play an important role in charge transfers. When that happens, work function of a sample is changed.

The Kelvin probe system allows precise measurement of work function of different semiconducting and conducting materials with high precision and accuracy.

The non-contact measurement involves oscillating capacitor, one electrode of which is a specimen, the other is oscillating reference electrode made of gold grid. Thus, measured value is referenced to the workfunction of gold (5.1 eV). Resolution of the measurement can reach 0.1 meV with sufficiently long integration time. The Kelvin probe system can be used in various type of surface studies, including: corrosion, adsorption/desorption, surface charging, catalytic activity and others.

For convenience, the probe is equipped with laser pointer and digital microscope. The motorized vertical positioning system allows reproducible of the reference electrode at the same distance from the specimen’s surface (with accuracy of 10 um). X-Y positioning can be installed as an option. The system is also equipped with wide-band light guide that can be coupled with digitally-controlled monochromator and high pressure xenon arc lamp. The wavelength range from 300 to 1000 nm can be used for continuous or pulsed sample illumination. This configuration allows measurement of the workfunction and electrical charging of surfaces, surface photovoltage spectroscopy and other photophysical techniques with photovoltage resolution better than 5 mV (0.1 mV when long integration time is applied). The whole system is accommodated in grounded Faraday cage for reduction of electrical noise and the influence of stray light. This surface photovoltage spectrometer is an essential tool in investigation of photocatalysts, organic and inorganic semiconductors, solar cells and other photoactive materials and devices. With the help of this Kelvin probe/surface photovoltage spectrometer monitoring of photocorrosion of semiconductors, photodesorption and photocatalytic reactions in real time is also possible.

Design
The device consists of an oscillating gold probe mounted on a firm stand with Z-axis motorized stage, electronic control units and a Faraday cage.

  • A sample is placed on manual or motorized XY-stage with motion range of 1.5 cm in either direction.
  • The probe is attached to a Z-stage that can place it at a desired distance from a sample.
  • A red laser pointer shows place where the probe will oscillate over during measurement .
  • A USB microscope and a white LED are helpful once the system is covered with a Faraday cage.
  • Light is delivered to the sample with liquid waveguide or optic fiber, so the possible EM interference from a light source is eliminated.
  • In idle run or during storage the fragile gold probe is homed into a protected space to prevent accidental damage.
  • The system is also equipped with the automatic sample height sensor.
Voltage range -5 V .. 5 V
Voltage measurement nominal resolution 0.15 mV
Measurement technology 2-channel lock-in amplifier
Sample holder translation stage X-Y, manual (default) or motorized
X-Y stage stroke 15 mm x 15 mm
Tip type Au mesh, dia. 2.5 mm
Tip Z positioning motorized Z stage
Positioning with respect to a sample light barrier
Tip Z positioning resolution 10 µm
Spectral range for wave guides 200 nm .. 2000 nm (depending on a waveguide)
Liquid waveguides selection (Lumatec)
Auxiliary sensors humidity and temperature
Internal Faraday cage illumination white LED
X-Y positioning aid laser sample placement indicator
PC connectivity USB 2.0
Size 40 x 40 x 45 cm
Weight 10 kg