VSS

• Provides sulfur flux rates for R&D applications on a DN40CF flange

• Flux regulation and on/off control by motorized valve

• UHV-tight valve

• Water-cooled cracker with beam shaping nozzle

• 12 cm³ or 150 cm³ reservoir

• Reservoir and valve are located ex vacuum

Data Sheet

The Valved Sulfur Source (VSS) aims at R&D applications where valve controlled small or medium flux rates of high vapor pressure materials are required.

This cell comes with a water-cooled cracker that reaches temperatures up to 1400°C. The cracker and injector building blocks are identical with our established TCC design. As shown for TCC, the thermal cross talk between the cracker and reservoir are almost negligible. See figure on the right for a schematic overview of the VSS cell. 

The reservoir and the valve are both located ex vacuum. This offers a huge benefit for reloading the reservoir or maintenance work, which can be done without venting the chamber. The reservoir and valve are heated by industrial grade electrical heaters and are both temperature controlled with high accurate Pt100 thermometers. In order to achieve the highest possible cleanliness all critical welds for the valve and reservoir are prepared by electron beam welding.

The VSS is designed for reservoir temperatures up to 250°C and works smoothly down to 100°C. The internal thermal design ensures ideal temperature gradients for trouble free operation. To ensure maximum process control this cell offers four independent heating circuits (reservoir, valve, pipe, cracker). However, depending on application the cell can be operated by using three circuits only.

The VSS is equipped with a high precision stepper motor that controls the valve. Hence, flux modulations in the order of two magnitudes are typically obtainable. For other applications pneumatic and manual valve control is also available.

There are two different valve types available for the VSS, namely a high throughput variation with higher overall throughput and one valve with smaller throughput but finer flux regulation characteristics. See the figure on the right for information about valve characteristic.

Application

A source concept like this is used for high vapor pressure materials, which form atom clusters. Typical evaporation elements are S and Se.

The in-vacuum length of the VSS is either 220 mm or 287 mm. Other in vacuum lengths are achievable using application specific spacers.

By default the cracker insert will be made from pyrolytic boron nitride, which will ensure efficient cracking for sulfur and selenium.

The following figure shows an example of a short operating cycle of the VSS.

Technical data

Schematic drawing of a Valved Sulfur Source VSS

(drawing shows VSS 40-150-51-KS-RV-MC)