IR system [project 075]

Description

The system is designed for IR measurements.

It consists of a main frame, frame for infrared analyser and three chambers with associated equipment. The IR analyser frame is independent and can be easily disconnected from the main frame and moved to another position in the laboratory.

The system can be extend in the future with the addition of other chambers or techniques e.g. MBE. The innovative design enables not only reflection-absorption infrared spectroscopy (RA-IRS) measurements at grazing incidence on well-defined, perfectly flat substrates, but also allows supports IR measurements in transmission mode for polycrystalline powder samples. The unique design permits exceptionally high-quality IR spectra with high sensitivity and long-term stability for substrates kept at temperatures between 100 K and 1000 K.

Specification

The load-lock chamber is pumped by a turbomolecular pump set to produce a base vacuum of better than 1 x 10^-8 mbar after bakeout. This chamber is used to transfer samples from atmosphere into the UHV system without affecting the vacuum in the distribution or measurement chamber. The samples are first mounted on a sample holder and then inserted into the load-lock mechanism by using a special, dedicated gripper tool

The distribution chamber is evacuated by an ion getter pump 300l/s and a titanium sublimation pump (TSP), the base pressure being

The unique configuration of the measurement chamber enables direct insertion into the modified sample chamber of the FTIR spectrometer, resulting in a very compact connection. The measurement chamber hosts a high precision sample manipulator. The manipulator has X, Y, Z translation and R1 rotation. It is designed to allow precise manual placement of samples by utilising micrometers (X and Y axes) or handwheels (Z axis). A rotary drive is applied to provide R1 rotation around the X axis. The manipulator can be upgraded to full motorisation in the future. A sample receiving station is mounted on the manipulator, which is equipped with electrical contacts for heating and temperature control (type K thermocouple). The sample receiving station also contains pneumatically operated heating and cooling switches. Sample heating is accomplished by making electrical connections to the sample holder at a pressure of ~3 bar. When the pressure rises to about 6 bar, a sapphire ball is pressed against a counterpart made from copper and is thus thermally attached to the sample holder. In this way the sample can be cooled down to temperatures of 100 K when using liquid nitrogen.
The innovative design of the manipulator allows not only for grazing-incidence reflection measurements on well-defined surfaces, but also for transmission measurements on oxide powder samples. For the latter type of experiments a specially designed sample holder is used. For this type of measurements the manipulator is rotated by 90°. This, together with a readjustment of the mirrors in the IR spectrometer, allows for measurements in transmission mode

In order to add more flexibility to the UHV/IR apparatus, a storage chamber is attached to one of the ports of the distribution chamber. This chamber provides UHV storage for up to six sample holders. One of the sample-receiving stations of the manipulator attached to this chamber provides electrical contacts for heating and temperature measurements.

The distribition chamber has several spare ports for future flexibility e.g. adding preparation chambers or an additional high-pressure chamber for carrying out experiments at elevated pressures.