The deposition chamber used in the current investigation contains a shroud that encompasses the inner walls of the chamber. This shroud is cooled with liquid nitrogen during deposition to trap gases in the chamber to minimize the chamber pressure and ensure the cleanest possible environment for the high-purity deposition of Si and Al. Liquid nitrogen cooling typically lowers the vacuum pressure by an order of magnitude during deposition. The walls of the deposition chamber are heated prior to any experiment to degas the walls as much as possible for optimal chamber cleanliness and lowest possible vacuum pressure.

The chamber has three ports available for electron beam evaporators. One of the evaporators is used for the thermal evaporation of Si. As well, there are four available ports for thermal effusion cells, one of which is used for the thermal evaporation of Al. In general, the materials to be evaporated are prepared prior to introducing the substrate by heating them to a temperature higher than the temperature at which they will be used during deposition. This permits removal of any impurities by degassing.

Once the substrate is introduced to the deposition chamber, it is loaded into a substrate holder/heater assembly (Fig. 4.7). The holder/heater has rotational and vertical manipulation capabilities to allow for range of motion required for adjusting the substrate position with respect to a RHEED gun for in situ surface analysis. The holder/heater assembly utilizes a grid of thin heated tantalum strips to resistively heat the substrate from behind. The temperature of the heater is monitored by a thermocouple temperature gauge. The holder/heater has been modified with a tantalum shield that permits a sufficient aperture of deposition from the two evaporation sources. The shield has been installed to prevent accidental shorting of the electrical circuitry by Al deposition.

A reflective high energy electron diffraction (RHEED) gun is present in the deposition chamber as previously described. In situ monitoring of substrate surface changes is a necessary capability to monitor surface structures and film quality in real time. The RHEED system utilizes an accelerating voltage range up to 20 KeV.

In addition to the mentioned components of the deposition chamber, a mass spectrometer is present to monitor vacuum cleanliness. A thermocouple vacuum pressure gauge is used to monitor initial pressures during rough pumping, and ion gauges to monitor high- to ultra-high vacuum pressures. The chamber is isolated from the neighboring analysis and preparation chamber by a Viton-sealed gate valve and pumped by a CryoTorr 10 cryopump and titantium sublimation filaments.