Evidence of periodic electric fields generated by Spatial separation of photogenerated electron-hole pairs in short-period InAs/GaSb type-II superlattices

AbstractThe effect of interface anisotropy on the electronic structure of InAs/GaSb type-II superlattices is exploited in the design of thin-layer superlattices for mid-IR detection threshold. The design is based on a theoretical envelope function model that incorporates the change of anion and cation species across InAs/GaSb interfaces, in particular, across the preferred InSb interface. The model predicts that a given threshold can be reached for a range of superlattice periods with InAs and GaSb layers as thin as a few monolayers. Although the oscillator strengths are predicted to be larger for thinner period superlattices, the absorption coefficients are comparable because of the compensating effect of larger band widths. However, larger intervalence band separations for thinner-period samples should lead to longer minority electron Auger lifetimes and higher operating temperatures in p-type SLs. In addition, the hole masses for thinner-period samples are on the order the free-electron mass rather than being effectively infinite for the wider period samples. Therefore, holes should also contribute to photoresponse. A number of superlattices with periods ranging from 50.6 to 21.2 Å for the 4 μm detection threshold were grown by molecular beam epitaxy based on the model design. Low temperature photoluminescence and photoresponse spectra confirmed that the superlattice band gaps remained constant at 330 meV although the period changed by the factor of 2.5. Overall, the present study points to the importance of interfaces as a tool in the design and growth of thin superlattices for mid-IR detectors for room temperature operation.

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One Pot Synthesis of Ternary MWCNTs/ZnO/Chitosan Nanocomposite for Enhanced Photocatalytic Degradation of Organic Dyes and Antibacterial Activity

10.21203/rs.3.rs-882501/v1 ◽

2021 ◽

Author(s):

Mitra Malekkiani ◽

Abbas Heshmati Jannat Magham ◽

Fateme Ravari ◽

Mehdi Dadmehr

Keyword(s):

Antibacterial Activity ◽

Organic Dyes ◽

Antibacterial Properties ◽

Photogenerated Electron ◽

Spatial Separation ◽

Electron Hole ◽

One Pot ◽

E Coli ◽

Ternary Nanocomposite ◽

Vis Spectroscopy

Abstract Developing a cheap, stable and effective photocatalyst is necessary for remediation of persistent organic pollutants. To address this challenge, we proposed a unique interfacial engineering technique and proper bandgap matching strategy to synthesize MWCNTs/ZnO/Chitosan ternary nanocomposite for effective photocatalytic application. The features of the prepared samples were determined by FESEM, TEM, EDX, elemental mapping, AFM, FT-IR, XRD, UV-Vis spectroscopy and BET surface analysis. The obtained results showed successful fabrication of synthesized nanocomposites. Degradation effect of nanostructures on methylene blue (MB) and antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis) pathogenic strains were investigated. The proposed photocatalytic mechanism illustrated the electron transfer facilitated by MWCNTs/ZnO/Chitosan structure which results in spatial separation of electron-hole pairs. Compared with ZnO and ZnO/Chitosan, the prepared MWCNTs/ZnO/Chitosan ternary nanocomposite showed high usage of UV illumination and superior separation of photogenerated electron-hole pairs. MWCNTs/ZnO/Chitosan illustrated outstanding increased photocatalytic activity on MB degradation efficiency of 98.76% after 20 mins. In addition, the ternary nanocomposite also exhibited remarkable bactericidal activity against gram-positive (S. aureus) and (B. subtilis) and gram-negative (E. coli) bacteria strains. Due to the obtained results, the prepared nanocomposite would be an efficient candidate photocatalyst with antibacterial properties.

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Short-period InAs∕GaSb type-II superlattices for mid-infrared detectors

Applied Physics Letters ◽

10.1063/1.2150269 ◽

2005 ◽

Vol 87 (26) ◽

pp. 261106 ◽

Cited By ~ 37

Author(s):

H. J. Haugan ◽

F. Szmulowicz ◽

K. Mahalingam ◽

G. J. Brown ◽

S. R Munshi ◽

...

Keyword(s):

Infrared Detectors ◽

Type Ii ◽

Mid Infrared ◽

Short Period ◽

Type Ii Superlattices

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Pushing the envelope to the maximum: Short-period InAs/GaSb type-II superlattices for mid-infrared detectors

Physica E Low-dimensional Systems and Nanostructures ◽

10.1016/j.physe.2005.12.072 ◽

2006 ◽

Vol 32 (1-2) ◽

pp. 289-292 ◽

Cited By ~ 10

Author(s):

H.J. Haugan ◽

F. Szmulowicz ◽

G.J. Brown ◽

B. Ullrich ◽

S. R Munshi ◽

...

Keyword(s):

Infrared Detectors ◽

Type Ii ◽

Mid Infrared ◽

Short Period ◽

Type Ii Superlattices

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Tunable Electronic Properties of Type-II SiS2/WSe2 Hetero-Bilayers

Nanomaterials ◽

10.3390/nano10102037 ◽

2020 ◽

Vol 10 (10) ◽

pp. 2037

Author(s):

Yue Guan ◽

Xiaodan Li ◽

Ruixia Niu ◽

Ningxia Zhang ◽

Taotao Hu ◽

...

Keyword(s):

Band Gap ◽

Electronic Properties ◽

Density Functional ◽

Photogenerated Electron ◽

Strain Range ◽

Band Alignment ◽

Type Ii ◽

Electron Hole ◽

Structural And Electronic Properties ◽

Indirect Band Gap

First-principle calculations based on the density functional theory (DFT) are implemented to study the structural and electronic properties of the SiS2/WSe2 hetero-bilayers. It is found that the AB-2 stacking model is most stable among all the six SiS2/WSe2 heterostructures considered in this work. The AB-2 stacking SiS2/WSe2 hetero-bilayer possesses a type-II band alignment with a narrow indirect band gap (0.154 eV and 0.738 eV obtained by GGA-PBE and HSE06, respectively), which can effectively separate the photogenerated electron–hole pairs and prevent the recombination of the electron–hole pairs. Our results revealed that the band gap can be tuned effectively within the range of elastic deformation (biaxial strain range from −7% to 7%) while maintaining the type-II band alignment. Furthermore, due to the effective regulation of interlayer charge transfer, the band gap along with the band offset of the SiS2/WSe2 heterostructure can also be modulated effectively by applying a vertical external electric field. Our results offer interesting alternatives for the engineering of two-dimensional material-based optoelectronic nanodevices.

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