Abstract
Single-crystalline alloy II-VI semiconductor nanostructures have been used as functional materials to propel photonic and optoelectronic device performance in a broad range of the visible spectrum. Their functionality depends on the stable modulation of the direct band gap (E<inf>g</inf>), which can be finely tuned by controlling the properties of alloy composition, crystallinity, and morphology. We report on the structural correlation of the optical band gap anomaly of quaternary alloy Cd<inf>x</inf>Zn<inf>1-x</inf>S<inf>y</inf>Se<inf>1-y</inf> single-crystalline nanostructures that exhibit different morphologies, such as nanowires (NWs), nanobelts (NBs), and nanosheets (NSs), and cover a wide range of the visible spectrum (E<inf>g</inf> = 1.96-2.88 eV). Using pulsed laser deposition, the nanostructures evolve from NWs via NBs to NSs with decreasing growth temperature. The effects of the growth temperature are also reflected in the systematic variation of the composition. The alloy nanostructures firmly maintain single crystallinity of the hexagonal wurtzite and the nanoscale morphology, with no distortion of lattice parameters, satisfying the virtual crystal model. For the optical properties, however, we observed distinct structure-dependent band gap anomalies: the disappearance of bowing for NWs and maximum and slightly reduced bowing for NBs and NSs, respectively. We tried to uncover the underlying mechanism that bridges the structural properties and the optical anomaly using an empirical pseudopotential model calculation of electronic band structures. From the calculations, we found that the optical bowings in NBs and NSs were due to residual strain, by which they are also distinguishable from each other: large for NBs and small for NSs. To explain the origin of the residual strain, we suggest a semiempirical model that considers intrinsic atomic disorder, resulting from the bond length mismatch, combined with the strain relaxation factor as a function of the width-to-thickness ratio of the NBs or NSs. The model agreed well with the observed optical bowing of the alloy nanostructures in which a mechanism for the maximum bowing for NBs is explained. The present systematic study on the structural-optical properties correlation opens a new perspective to understand the morphology- and composition-dependent unique optical properties of II-VI alloy nanostructures as well as a comprehensive strategy to design a facile band gap modulation method of preparing photoconverting and photodetecting materials.
| Original language | English |
|---|---|
| Pages (from-to) | 5486-5499 |
| Number of pages | 14 |
| Journal | ACS Nano |
| Volume | 9 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 2015 May 26 |
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Keywords
- band gap bowing
- band gap modulation
- chalcogenide
- empirical pseudopotential method
- II-VI chemical compound semiconductor
- nanobelts
- nanosheets
- nanowires
- pulsed laser deposition
- quaternary alloy
ASJC Scopus subject areas
- Engineering(all)
- Materials Science(all)
- Physics and Astronomy(all)
Cite this
Structural origin of the band gap anomaly of quaternary alloy Cd<inf>x</inf>Zn<inf>1-x</inf>S<inf>y</inf>Se<inf>1-y</inf> nanowires, nanobelts, and nanosheets in the visible spectrum. / Kwon, S. Joon; Jeong, Hae Min; Jung, Kinam; Ko, Doo Hyun; Ko, Hyungduk; Han, Il Ki; Kim, Gyu-Tae; Park, Jae Gwan.
In: ACS Nano, Vol. 9, No. 5, 26.05.2015, p. 5486-5499.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Structural origin of the band gap anomaly of quaternary alloy CdxZn1-xSySe1-y nanowires, nanobelts, and nanosheets in the visible spectrum
AU - Kwon, S. Joon
AU - Jeong, Hae Min
AU - Jung, Kinam
AU - Ko, Doo Hyun
AU - Ko, Hyungduk
AU - Han, Il Ki
AU - Kim, Gyu-Tae
AU - Park, Jae Gwan
PY - 2015/5/26
Y1 - 2015/5/26
N2 - Single-crystalline alloy II-VI semiconductor nanostructures have been used as functional materials to propel photonic and optoelectronic device performance in a broad range of the visible spectrum. Their functionality depends on the stable modulation of the direct band gap (Eg), which can be finely tuned by controlling the properties of alloy composition, crystallinity, and morphology. We report on the structural correlation of the optical band gap anomaly of quaternary alloy CdxZn1-xSySe1-y single-crystalline nanostructures that exhibit different morphologies, such as nanowires (NWs), nanobelts (NBs), and nanosheets (NSs), and cover a wide range of the visible spectrum (Eg = 1.96-2.88 eV). Using pulsed laser deposition, the nanostructures evolve from NWs via NBs to NSs with decreasing growth temperature. The effects of the growth temperature are also reflected in the systematic variation of the composition. The alloy nanostructures firmly maintain single crystallinity of the hexagonal wurtzite and the nanoscale morphology, with no distortion of lattice parameters, satisfying the virtual crystal model. For the optical properties, however, we observed distinct structure-dependent band gap anomalies: the disappearance of bowing for NWs and maximum and slightly reduced bowing for NBs and NSs, respectively. We tried to uncover the underlying mechanism that bridges the structural properties and the optical anomaly using an empirical pseudopotential model calculation of electronic band structures. From the calculations, we found that the optical bowings in NBs and NSs were due to residual strain, by which they are also distinguishable from each other: large for NBs and small for NSs. To explain the origin of the residual strain, we suggest a semiempirical model that considers intrinsic atomic disorder, resulting from the bond length mismatch, combined with the strain relaxation factor as a function of the width-to-thickness ratio of the NBs or NSs. The model agreed well with the observed optical bowing of the alloy nanostructures in which a mechanism for the maximum bowing for NBs is explained. The present systematic study on the structural-optical properties correlation opens a new perspective to understand the morphology- and composition-dependent unique optical properties of II-VI alloy nanostructures as well as a comprehensive strategy to design a facile band gap modulation method of preparing photoconverting and photodetecting materials.
AB - Single-crystalline alloy II-VI semiconductor nanostructures have been used as functional materials to propel photonic and optoelectronic device performance in a broad range of the visible spectrum. Their functionality depends on the stable modulation of the direct band gap (Eg), which can be finely tuned by controlling the properties of alloy composition, crystallinity, and morphology. We report on the structural correlation of the optical band gap anomaly of quaternary alloy CdxZn1-xSySe1-y single-crystalline nanostructures that exhibit different morphologies, such as nanowires (NWs), nanobelts (NBs), and nanosheets (NSs), and cover a wide range of the visible spectrum (Eg = 1.96-2.88 eV). Using pulsed laser deposition, the nanostructures evolve from NWs via NBs to NSs with decreasing growth temperature. The effects of the growth temperature are also reflected in the systematic variation of the composition. The alloy nanostructures firmly maintain single crystallinity of the hexagonal wurtzite and the nanoscale morphology, with no distortion of lattice parameters, satisfying the virtual crystal model. For the optical properties, however, we observed distinct structure-dependent band gap anomalies: the disappearance of bowing for NWs and maximum and slightly reduced bowing for NBs and NSs, respectively. We tried to uncover the underlying mechanism that bridges the structural properties and the optical anomaly using an empirical pseudopotential model calculation of electronic band structures. From the calculations, we found that the optical bowings in NBs and NSs were due to residual strain, by which they are also distinguishable from each other: large for NBs and small for NSs. To explain the origin of the residual strain, we suggest a semiempirical model that considers intrinsic atomic disorder, resulting from the bond length mismatch, combined with the strain relaxation factor as a function of the width-to-thickness ratio of the NBs or NSs. The model agreed well with the observed optical bowing of the alloy nanostructures in which a mechanism for the maximum bowing for NBs is explained. The present systematic study on the structural-optical properties correlation opens a new perspective to understand the morphology- and composition-dependent unique optical properties of II-VI alloy nanostructures as well as a comprehensive strategy to design a facile band gap modulation method of preparing photoconverting and photodetecting materials.
KW - band gap bowing
KW - band gap modulation
KW - chalcogenide
KW - empirical pseudopotential method
KW - II-VI chemical compound semiconductor
KW - nanobelts
KW - nanosheets
KW - nanowires
KW - pulsed laser deposition
KW - quaternary alloy
UR - http://www.scopus.com/inward/record.url?scp=84930620461&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84930620461&partnerID=8YFLogxK
U2 - 10.1021/acsnano.5b01472
DO - 10.1021/acsnano.5b01472
M3 - Article
AN - SCOPUS:84930620461
VL - 9
SP - 5486
EP - 5499
JO - ACS Nano
JF - ACS Nano
SN - 1936-0851
IS - 5
ER -