High Performance BiOCl Nanosheets/TiO₂ Nanotube Arrays Heterojunction UV Photodetector: The Influences of Self‐Induced Inner Electric Fields in the BiOCl Nanosheets

Abstract

BiOCl nanosheets/TiO2 nanotube arrays heterojunction UV photodetector (PD) with high performance is fabricated by a facile anodization process and an impregnation method. The heterojunction at the interface and the internal electric fields in the BiOCl nanosheets faciliate the separation of photogenerated charge carriers and regulate the transportation of the electrons. Compared with the large dark current (≈10−5 A), low on/off ratio (8.5), and slow decay time (>60 s) of the TiO2 PD, the optimized heterojunction PD (6‐BiOCl–TiO2) yields dramatically decreased dark current (≈1 nA), ultrahigh on/off ratio (up to 2.2 × 105), and fast decay speed (0.81 s) under 350 nm light illumination at −5 V. Moreover, it exhibits an increased responsivity of 41.94 A W−1, a remarkable detectivity (D*) of 1.41 × 1014 Jones, and a high linear dynamic range of 103.59 dB. The loading amount and growth orientations of the BiOCl nanosheets alter the roles of the self‐induced internal electric field in regulating the behaviors of the charge carriers, thus affecting the photoelectric properties of the heterojunction PDs. These results demonstrate that rational construction of novel heterojunctions hold great potentials for fabricating photodetectors with high performance.

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

“…Similar plasmonic excitations were observed also by Crassee et al [208] on epitaxial single layer graphene on 6H-SiC. 2020, 8,1900623 [41]: strong quasimonochromatic linearly polarized light with a peak field of up to 85 kV cm −1 is incident on a graphene sample with E F = 170 meV and τ = 47 fs; the generated odd-order harmonics are detected in transmission geometry using electro-optic sampling. The plasma modes can be easily controlled by magnetic field owing to the small cyclotron mass of Dirac fermions.…”

“…For example, thermal decomposition of SiO x layers produces networks of silicon NCs; by varying the oxygen content (x) of the layers, it is possible to tune the density and, in turn, also the percolation degree of the NC network. 2020, 8,1900623 (11). For lower x, the Drude-Smith localization parameter c 1 is significantly above −1 but it tends to more negative values with increasing pump-probe delay, which was explained by progressive carrier localization caused by the development of Schottkytype barriers as carriers are trapped at the interfaces, [117,118] see also Figure 7.…”

“…At room temperature NC sizes corresponding to f c = 1 THz are in the range of hundreds of nanometers in semiconductors with small electron effective mass (e.g., 250 nm in GaAs) and a few tens of nanometers in materials with huge effective mass (e.g., ≈25 nm in rutile). 2020, 8,1900623 Figure 1. Thanks to the development of THz technologies, it is thus nowadays possible to carry out such studies experimentally.…”

“…[2,3] Nanowires and nanotubes made of conventional semiconductors are quasi 1D systems combining Terahertz spectroscopy has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes or 2D crystals. [7,8] The dimensions can be pushed further down toward the molecular level. In addition, probing of photoinitiated ultrafast charge dynamics is possible thanks to the sub-picosecond time resolution.…”

“…2020,8, 1900623 The curves with the exception of the Drude-Smith model are entirely determined by the size and microscopic properties of NCs: we consider here GaAs cubes at 300 K with a momentum scattering time of 270 fs.…”