Award Date

1-1-2007

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

First Committee Member

Rama Venkat

Number of Pages

90

Abstract

10Boron (10B) is an isotope of Boron. 10B and neutron interaction yields alpha particles. alpha particles typically deposit their energy within a few tenths of nanometers within a semiconductor creating electron-hole pairs which through radiative recombination yield photon emission of band gap energy. The number of photons emitted directly relates to the energy and flux density of incoming neutron. Thus, 10B coated semiconductors can be used as a neutron detectors. 10B is an expensive material, especially in the disc and the powdered form which is needed for sputtering. Since a hemispherical target of 10B of diameter 4.8cm was available, a sputter source was designed and built around this target. The design was based on various electrostatic and magnetostatic analysis from TRICOMP 6.0 (Finite Element Software for Electromagnetics), SOLIDWORKS 2006 (3 D Mechanical Design Software) and previous experience with sputtering systems and vacuum systems. The vacuum chamber was evacuated by an unthrottled turbomolecular pump backed by an oil sealed mechanical pump. The target head consists of 10B, cylindrical soft iron housing with a glass ring to prevent sputtering of iron from the stainless steel ring and Neodymium-Iron-Boron permanent magnet. Thin films of 10B were deposited on silicon wafer and were characterized for its chemical composition and thickness using X-ray fluorescence spectroscopy and Scanning electron Microscope. The growth rate was in the range of 0.046A/sec. The deposited film contained 10B in the range of 19.46%, carbon in the range of 1.31% and copper in the range of 14.21%. In addition to all these elements, the films contained 65% of oxygen. Despite the fact that the system was leak tight (as determined by a quadrupole mass analyzer), the presence of oxygen in the deposited films could not be avoided. This was due to residual water vapor and our necessarily low deposition rate. This was further ascertained by a theoretical calculation based on RGA measurements and growth rate. Possible improvements to system are: rotating the substrate to improve spatial thickness uniformity, cooling the sputter head so that the deposition rate can be increased and changing the rubber o-ring so that the system can be baked to minimize oxygen incorporation in the film.

Keywords

Boron; Design; Hemispherical; Sputtering; System; Target

Controlled Subject

Electrical engineering

File Format

pdf

File Size

4976.64 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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