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Influence of vacancy defect on surface feature and adsorption of Cs on GaN(0001) surface.

Ji Y, Du Y, Wang M - ScientificWorldJournal (2014)

Bottom Line: The covalent bonds gain strength for Ga vacancy defect, whereas they grow weak for N vacancy defect.The lower work function is achieved for Ga and N vacancy defect surfaces than intact surface.The most stable position of Cs adatom on Ga vacancy defect surface is at T1 site, whereas it is at B(Ga) site on N vacancy defect surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Optoelectronic Engineering, Binzhou University, Binzhou 256603, China.

ABSTRACT
The effects of Ga and N vacancy defect on the change in surface feature, work function, and characteristic of Cs adsorption on a (2 × 2) GaN(0001) surface have been investigated using density functional theory with a plane-wave ultrasoft pseudopotential method based on first-principles calculations. The covalent bonds gain strength for Ga vacancy defect, whereas they grow weak for N vacancy defect. The lower work function is achieved for Ga and N vacancy defect surfaces than intact surface. The most stable position of Cs adatom on Ga vacancy defect surface is at T1 site, whereas it is at B(Ga) site on N vacancy defect surface. The E(ads) of Cs on GaN(0001) vacancy defect surface increases compared with that of intact surface; this illustrates that the adsorption of Cs on intact surface is more stable.

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Top view of various possible adsorption sites of Cs on 2 × 2 GaN(0001) defect surface: (a) Cs on Ga defect surface, (b) Cs on N defect surface.
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fig2: Top view of various possible adsorption sites of Cs on 2 × 2 GaN(0001) defect surface: (a) Cs on Ga defect surface, (b) Cs on N defect surface.

Mentions: One Ga atom or one N atom on the outmost layer of 2 × 2 GaN(0001) surface was removed in researching vacancy defect surface, respectively (shown in Figure 1). Figure 1(a) shows the side view of Ga vacancy defect surface and (c) is the top view. Figure 1(b) shows the side view of N vacancy defect surface and (d) is the top view. For a Cs adsorption on GaN(0001) surface, five typical adsorption models including sites of T1 (Ga top), H3 (hollow site), T4 (N top), BGa (Ga bridge), and BN (N bridge) were chosen [34, 35]. In this paper, these five typical adsorption sites are adopted to study the influence of Ga and N vacancy defects on the adsorption of Cs on GaN(0001) surface. Figure 2 shows the top view of Cs at T1, H3, T4, BGa, and BN sites on GaN(0001) defect surface. Figure 2(a) shows the top view of Cs on Ga vacancy defect surface and Figure 2(b) is Cs on N vacancy defect surface.


Influence of vacancy defect on surface feature and adsorption of Cs on GaN(0001) surface.

Ji Y, Du Y, Wang M - ScientificWorldJournal (2014)

Top view of various possible adsorption sites of Cs on 2 × 2 GaN(0001) defect surface: (a) Cs on Ga defect surface, (b) Cs on N defect surface.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4121101&req=5

fig2: Top view of various possible adsorption sites of Cs on 2 × 2 GaN(0001) defect surface: (a) Cs on Ga defect surface, (b) Cs on N defect surface.
Mentions: One Ga atom or one N atom on the outmost layer of 2 × 2 GaN(0001) surface was removed in researching vacancy defect surface, respectively (shown in Figure 1). Figure 1(a) shows the side view of Ga vacancy defect surface and (c) is the top view. Figure 1(b) shows the side view of N vacancy defect surface and (d) is the top view. For a Cs adsorption on GaN(0001) surface, five typical adsorption models including sites of T1 (Ga top), H3 (hollow site), T4 (N top), BGa (Ga bridge), and BN (N bridge) were chosen [34, 35]. In this paper, these five typical adsorption sites are adopted to study the influence of Ga and N vacancy defects on the adsorption of Cs on GaN(0001) surface. Figure 2 shows the top view of Cs at T1, H3, T4, BGa, and BN sites on GaN(0001) defect surface. Figure 2(a) shows the top view of Cs on Ga vacancy defect surface and Figure 2(b) is Cs on N vacancy defect surface.

Bottom Line: The covalent bonds gain strength for Ga vacancy defect, whereas they grow weak for N vacancy defect.The lower work function is achieved for Ga and N vacancy defect surfaces than intact surface.The most stable position of Cs adatom on Ga vacancy defect surface is at T1 site, whereas it is at B(Ga) site on N vacancy defect surface.

View Article: PubMed Central - PubMed

Affiliation: Department of Optoelectronic Engineering, Binzhou University, Binzhou 256603, China.

ABSTRACT
The effects of Ga and N vacancy defect on the change in surface feature, work function, and characteristic of Cs adsorption on a (2 × 2) GaN(0001) surface have been investigated using density functional theory with a plane-wave ultrasoft pseudopotential method based on first-principles calculations. The covalent bonds gain strength for Ga vacancy defect, whereas they grow weak for N vacancy defect. The lower work function is achieved for Ga and N vacancy defect surfaces than intact surface. The most stable position of Cs adatom on Ga vacancy defect surface is at T1 site, whereas it is at B(Ga) site on N vacancy defect surface. The E(ads) of Cs on GaN(0001) vacancy defect surface increases compared with that of intact surface; this illustrates that the adsorption of Cs on intact surface is more stable.

Show MeSH