Pressure Impact on the Crystal Structure, Optical, and Transport Properties in Layered Oxychalcogenides BiCuChO (Ch = S, Se)

Abstract

The layered oxychalcogenides BiCuChO (Ch = S, Se, Te) represent a unique family of two-dimensional semiconductors with extraordinary optoelectronic and thermoelectric properties. Chemical strategies such as elemental doping have been used to modify their crystal structures and electronic configurations for better photocatalytic performances. Herein, we report the pressure impact on the crystalline and electronic band structures of BiCuChO (Ch = S, Se) with in situ synchrotron X-ray diffraction, Raman spectroscopy, electric resistivity and photocurrent measurements, and first-principle calculations. Under pressure, the crystalline lattices shrink continuously without symmetry breaking, which enhances the crystal field splitting; on the other hand, the pressure-induced charge delocalization causes the band broadening. The competition between the crystal field and charge delocalization demonstrates an efficient tool for band gap engineering: the electrical conductivity is enhanced below 12 GPa and monotonically decreases up to 40 GPa. In addition, BiCuSeO exhibits considerable photocurrent up to ∼40 GPa, which suggests its potential application in pressure-responsive optoelectrical devices. The comprehensive studies of the pressure effect on the crystal structure and electronic properties in two-dimensional semiconductors provide and in-depth understanding for developing new optoelectronic materials under extreme conditions.

Lattice Dynamics Study of Thermoelectric Oxychalcogenide BiCuChO (Ch = Se, S)

“…Figure 2 shows a comparison of the experimental Raman spectra of BiCuSeO and BiCuSO recorded at room temperature between 30 and 500 cm −1 . These spectra are in good agreement with the spectra at ambient conditions in the recent work of Zhang et al 28 In the case of BiCuSeO, four strong lines can be observed located at 55, 85, 147, and 177 cm −1 . They correspond to the four Raman M1−M4 modes found by Zhang et al 28 The two tiny features at 102 and 113 cm −1 are not significant because their magnitudes are comparable to the background noise.…”

“…20 To discriminate between these different possibilities and understand the origin of the intrinsically low thermal conductivity in BiCuSeO and related compounds, the study of the experimental lattice dynamics in BiCuChO compounds is of fundamental interest. However, to our knowledge, there is only one infrared spectroscopic study of the lattice vibrations of BiCuSeO 27 and one very recent Raman spectroscopic study of the lattice vibrations of both compounds; 28 both have been reported at room temperature. In this Raman study, the assignment of the Raman modes of BiCuSeO is made following the calculations of Saha, 14 whereas that of BiCuSO was made without the support of any theoretical study.…”

Ethanol Guerbet Condensation to n‐Butanol or C4‐C8 Alcohols over Ni/TiO2 Catalyst

“…And esterification of acetic acid separately with n-butanol and 2ethylbutanol takes place to produce butyl acetate and 2-ethylbutyl acetate (reactions 17 and 18). [21,22]…”

Electrochemical (Bio)sensing of Clinical Markers Using Quantum Dots

“…A different way to use QDs in an electrochemical DNA sensor has been considered by Zhang et al. for the detection of specific DNA sequences of bladder cancer cells. In this work, QDs are not used as signal tags, but as modifiers on the GCE transducer surface.…”