Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...
Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...
Analysis of the extended defects in 3C-SiC.pdf - Nelson Mandela ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
2.1. Introduction<br />
3<br />
CHAPTER TWO<br />
OVERVIEW OF CRYSTAL DEFECTS IN <strong>3C</strong>-<strong>SiC</strong><br />
In this chapter a short overview <strong>of</strong> <strong>the</strong> types <strong>of</strong> crystal <strong>defects</strong> found <strong>in</strong> <strong>3C</strong>-<strong>SiC</strong> is<br />
presented. The content presented is by no means complete but focuses on <strong>the</strong><br />
important aspects needed to understand <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> experimental results later<br />
on. The reader is advised to consult o<strong>the</strong>r references written specifically for this<br />
purpose if a deeper understand<strong>in</strong>g is required (Hull et al. (1984)). This chapter<br />
focuses ma<strong>in</strong>ly on <strong>the</strong> <strong>defects</strong> found <strong>in</strong> <strong>the</strong> z<strong>in</strong>c-blende structure s<strong>in</strong>ce this is <strong>the</strong><br />
crystal structure <strong>of</strong> <strong>3C</strong>-<strong>SiC</strong>. The structure itself is expla<strong>in</strong>ed firstly by referr<strong>in</strong>g to a<br />
more simple structure i.e. <strong>the</strong> fcc structure with special attention given to <strong>the</strong> atomic<br />
stack<strong>in</strong>g sequences <strong>in</strong> <strong>the</strong> pr<strong>in</strong>cipal crystallographic directions. Fur<strong>the</strong>rmore <strong>the</strong> types<br />
<strong>of</strong> po<strong>in</strong>t <strong>defects</strong> found <strong>in</strong> <strong>SiC</strong> are discussed and <strong>the</strong>ir diffusion characteristics are<br />
reviewed. F<strong>in</strong>ally <strong>the</strong> nature <strong>of</strong> <strong>the</strong> <strong>extended</strong> <strong>defects</strong> present <strong>in</strong> <strong>3C</strong>-<strong>SiC</strong> is discussed.<br />
2.2. Cubic and Z<strong>in</strong>c-Blende Crystal Structures<br />
2.2.1 The Face-Centred Cubic Structure<br />
The unit cell <strong>of</strong> <strong>the</strong> face-centred cubic (fcc) structure is a cube with atoms situated at<br />
<strong>the</strong> corners and centres <strong>of</strong> <strong>the</strong> cube faces as illustrated <strong>in</strong> Fig. 2.1. It conta<strong>in</strong>s four<br />
1<br />
atoms <strong>in</strong> positions 000 ; 0<br />
1 1<br />
2 2 ; 2 2<br />
1 1 1<br />
0 and 0 2 2 , with <strong>the</strong> smallest translation vectors<br />
be<strong>in</strong>g <strong>of</strong> <strong>the</strong> type (1/2). This corresponds to half a surface diagonal <strong>of</strong> <strong>the</strong> unit<br />
cell.