Advanced Materials Research Laboratory

The STM-CVD system

The system, shown below, was originally developed under the HEFCW DevR Intiative for the study of ZnSe growth onto GaAs substrates. Costing some 200k in parts alone, this all-metal CVD system is unique within the U.K.  Links between UHV growth systems such as Molecular Beam Epitaxy (MBE) to surface science systems have been developed in many laboratories around the world but only recently has such a link been achieved to a chemical vapour deposition system where the ambient pressures for materials growth are much higher (up to one atmosphere) than for MBE.

Our system combines an STM and LEED (Low energy electron diffraction) operating in Ultra High Vacuum (UHV) together with a sample manipulator. The latter has a built-in heater capable of reaching 1200 degrees C. The laminar flow reactor has at present a cartridge heater capable of temperatures around 950 degrees C.

The gas handling system (and reactor) is enclosed within a protective cabinet and is made by Electro-Gas Systems Ltd. The STM is a STM1 by Omicron GmbH while the LEED is manufactured by VG Ltd. A Hiden  Analytical Residual Gas Analyser (RGA) is fitted to the sample transfer system. The RGA is essential for monitoring the levels of contaminants after or during sample transfer. The mounting frame, reactor and sample transfer chambers were constructed by Scanwel Ltd. (Bala, Gwynedd).

The birds-eye view of the original system seen above shows the STM mini-chamber at lower middle-left (large viewport) while the LEED camera sits far left. The reactor chamber, top middle, sits within the gas handling cabinet and is linked to the UHV side via two magnetic transfer arms. The RGA system is the small dark box attached to the transfer chamber in the center.

For research into carbon nanotubes, a new, custom designed CVD cabinet has been supplied by Electro-Gas Systems Ltd enabling better access to the CVD reactor. Further modifications have been included to enable much higher growth temperatures (950C). The images below show the new system.

A view from the front is shown below. An Advanced Energy MDX1k DC PSU sits atop the cabinet for plasma-assisted CVD growth. Below it on the front panel is the four-channel gas flow control (MKS Inc.) and the Land Systems optical pyrometer.

The Omicron sample carrier can be seen here during carbon nanotube growth at 900C. The sample chips (8x8 mm) are clamped onto the molybdenum plate using a 0.005" Mo foil with custom Mo screws.

Latest news

We have rebuilt and extended the system with a separate cabinet enclosure to house a larger area reactor unconnected to the UHV system. The new reactor will be capable of holding 2" wafer sizes or multiple numbers of smaller chips. The reactor can be used for both thermal and plasma-assisted growth. A photo of the new system is shown below. It shares the same gas handling system as the UHV reactor.