High-pressure RHEED extension

Reflection High-Energy Electron Diffraction (RHEED) is in principle incompatible with high-pressure depostion techniques, like Pulsed Laser Depostion. Due to the relatively high pressures (up to 1 mbar/1 Torr), the electron are scattered and the image is lost. By adding an extension to a standard RHEED-gun and phosphor screen system, these problems can be avoided.

Twente Solid State Technology designs, produces and implements PLD-RHEED systems for high-pressure environments. Furthermore, advice and help to adapt existing PLD-chambers for high-pressure RHEED are given.

The extension consists of two parts: a tube to guide the electrons coming from the gun and a tubular flange to which the phosphor screen is attached.

The phosphor screen flange is extending into the vacuum chamber to be placed as close as possible to the substrate surface. Due to this effect the RHEED-images will be reduced in size (5x5 mm², or 0.2x0.2 sq.inch) as compared to normally obtained images. Furthermore, the screen is equipped with a shield to avoid deposition on the screen as much as possible.

For every costumer the design will be fully adapted to any existing deposition system. In addition advice and technical support to implement the RHEED-extension are included.

The standard system can be extended with the following two options:

A valve to close the tube during near-atmospheric anneal. This way the pump, pumping the extension tube does not have to be switched off.
A shutter to protect the phosphor screen from contamination during depostion without RHEED-imaging.

Technical Specifications

System pressures up to 0.5 mbar (400 mTorr)
Pressure in tube: <10^-3 mbar (0.75 mTorr)
Total travelling distance for electrons in high-pressure region: ~ 10 cm (4")