Abstract
The adsorption and migration of sulphur (S) atoms on the diamond (001) surface were investigated through first principles calculations to discover the inherent law in S-doped diamond film growth. Results indicated that deposited S atoms could abstract the hydrogen atom on the surface. The adsorption energies were in a range of 2.47 to 5.5 eV when S atoms were deposited on the hydrogen terminated surface or the surface with open radical sites (ORSs). The S atom could migrate on the surface of the 3ORS slabs and the energy barrier was approximately 1.35 eV. The calculations of the projected density of states and the analysis of the magnetic moments presented an interesting result, which demonstrated the evolving phenomena in S-doped diamond film growth and discovered the inherent laws. On the 2ORS slabs, the magnetic moment of the S atom became 0.000 μB after bonding with the two carbon atoms. In such case, a new doped C atom combined with the S atom with a triple bond, and then the C–S molecule was desorbed from the surface. The abstraction of the adsorbed S atom results from the fact that S atoms have six electrons in their outermost electron shell. This finding revealed the reason behind the low S incorporation and the growth rate decrease in S-doped diamond film deposition. This discovery also indicated that atoms with six electrons in their outermost electron shell might hardly be doped into the diamond films during the deposition process.
Highlights
Sulphur (S)-doped diamond films were studied for many applications, such as n-type semiconductors [1,2,3], electron emission from nano-structured materials [4], field emission for cold cathode devices [5], and hard coatings [6].S-doped diamond films were studied as shallow-donor dopants for n-type diamond semiconductors
The abstraction of the adsorbed S atom results from the fact that S atoms have six electrons in their outermost electron shell. This finding revealed the reason behind the low S incorporation and the growth rate decrease in S-doped diamond film deposition
S-shallow donors with activation energy of 0.38 eV were found [7,8] to be connected to boron, which was accidentally added through chemical vapor depositions (CVD) reactor contamination [9]
Summary
Sulphur (S)-doped diamond films were studied for many applications, such as n-type semiconductors [1,2,3], electron emission from nano-structured materials [4], field emission for cold cathode devices [5], and hard coatings [6]. One research showed that the growth rate of diamond films could slightly increase via S doping at a low deposit temperature (700 ◦ C) [12]. Studied the equilibrium geometry and the band structure of S-doped diamond using density functional theory (DFT) calculations. Their result indicated that S atoms were spontaneously incorporated into the diamond (100) surface [10]. The first-principles calculations in our previous studies were conducted to study the doped diamond films and the adsorption and migration of Si, boron (B), yttrium (Y), niobium (Nb), and nitrogen (N) atoms on the diamond (001) surface [16,17,18,19,20,21,22,23]. The adsorption and migration of S atoms on the diamond (001) surface were investigated in this study
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