Excitonic and electronic transitions in Me–Sb 2 Se 3 structures

• Published in: Beilstein journal of nanotechnology Vol. 11; pp. 1045 - 1053
• Main Authors: Syrbu, Nicolae N, Zalamai, Victor V, Stamov, Ivan G, Beril, Stepan I
• Format: Journal Article
• Language: English
• Published: 16-07-2020
• ISSN: 2190-4286; 2190-4286
• DOI: 10.3762/bjnano.11.89

The optical anisotropy of the Sb
2
Se
3
crystals was investigated at 300 and 11 K. Excitonic features of four excitons (A, B, C, and D) were observed in the optical spectra of the Sb
2
Se
3
single crystals and in the photoelectric spectra of the Me–Sb
2
Se
3
structures. The exciton parameters, such as the ground (
n
= 1) and excited (
n
= 2) state positions and the binding energy (Ry), were determined. The effective mass of the electrons at the bottom of the conduction band (
m
c
*
= 0.67
m
0
) as well as the holes at the four top valence bands (
m
v1
*
= 3.32
m
0
,
m
v2
*
= 3.83
m
0
,
m
v3
*
= 3.23
m
0
and
m
v4
*
= 3.23
m
0
) were calculated in the Г-point of the Brillouin zone. The magnitude of the valence band splitting V
1
–V
2
due to the spin–orbit interaction (Δ
so
= 35 meV) and the crystal field (Δ
cf
= 13 meV) were estimated in the Brillouin zone center. The energy splitting between the bands V
3
–V
4
was 191 meV. The identified features were discussed based on both the theoretically calculated energy band structure and the excitonic band symmetry in the Brillouin zone (
k
= 0) for crystals with an orthorhombic symmetry (
Рnma
). The photoelectric properties of the Me–Sb
2
S
3
structures were investigated in the spectral range 1–1.8 eV under
E
||c and
E
⟂c polarization conditions and at different applied voltages.