THE APPLICATION OF A SUPERSONIC MOLECULAR BEAM SCATTERING SYSTEM TO UNDERSTANDING CVD PROCESSES

A detailed description of a supersonic molecular beam scattering system for investigating surface processes involved in chemical vapour deposition (CVD) is given. The system can be used for both the carrying out of depositions and the simultaneous study of reaction mechanisms using modulated molecular beam relaxation spectroscopy and other surface science techniques. The advantages of this system for real time in-situ analysis of reaction mechanisms compared to previous approaches are discussed. The application of this system to the deposition and study of GaAs is discussed. With the increasing demand for improved layer quality, it is becoming more important to develop, control and understand the new generation of CVD processes

Symmetry and phase-selected NMR spectra of liquid crystalline samples

It is demonstrated that the NMR spectra of liquid crystalline samples can be simplified by using multiple quantum filtering. In a system of N spin-Image nuclei, the N or (N-1)-multiple quantum filtered spectra (NQF or (N-1)QF) contain lines which originate only from transitions among the eigenstates belonging to the highest symmetry class of the spin permutation group. In addition the NQF spectra are divided further into two sets of lines which differ in phase by 180°. A method for simulating and analysing multiple quantum filtered spectra is described, with examples from molecules with up to eight interacting spins