Dong Li,Guanjie Xing,Shilin Tang,Xiaohong Li,Louzhen Fan,Yunchao Li
We report herein a heat-triggered precursor slow releasing route for the one-pot synthesis of ultrathin ZnSe nanowires (NWs), which relies on the gradual dissolving of Se powder into oleylamine containing a soluble Zn precursor under heating. This route allows the reaction system to maintain a high monomer concentration throughout the entire reaction process, thus enabling the generation of ZnSe NWs with diameter down to 2.1 nm and length approaching 400 nm. The size-dependent optical properties and band-edge energy levels of the ZnSe NWs were then explored in depth by UV-visible spectroscopy and cyclic voltammetry, respectively. Considering their unique absorption properties, these NWs were specially utilized for fabricating photoelectrochemical-type photodetectors (PDs). Impressively, the PDs based on the ZnSe NWs with diameters of 2.1 and 4.5 nm exhibited excellent responses to UVA and near-visible light, respectively: both possessed ultrahigh on/off ratios (5150 for UVA and 4213 for near-visible light) and ultrawide linear response ranges (from 2.0 to 9000 μW cm−2 for UVA and 5.0 to 8000 μW cm−2 for near-visible light). Furthermore, these ZnSe NWs were selectively doped with various amounts of Mn2+ to tune their emission properties. As a result, ZnSe NW film-based photochromic cards were creatively developed for visually detecting UVA and near-visible radiation.
Single-crystal p-type ZnSe nanowires (NWs) with zinc blende structure and [21–1] growth direction were synthesized by using bismuth (Bi) as dopant via a thermal co-evaporation method. The ZnSe : Bi NWs showed evident p-type conductivity with hole concentration up to 4.1 × 1018 cm−3 after the acceptor activation. Negative photoconductivity was first investigated in the p-ZnSe NWs, i.e., the conductivity of the NWs under light was dramatically lower than that in the dark. Surface effects arising from oxygen absorption and photo-desorption were suggested to be responsible for this. By using Al as the Schottky gate, high-performance nano-metal-semiconductor field-effect transistors (nanoMESFETs) were constructed, and measurements on the Al/p-ZnSe NW Schottky diode also revealed the bias-dependent photoresponse. It is expected that the p-type ZnSe : Bi NWs will have great potential in nano-optoelectronic applications.
In this work, we combine the catalytic growth and ligand control mechanisms to synthesize ultrathin/ultralong ZnSe nanowires (NWs). Ag 2 Se catalyst seeds initiate the NW growth and significantly cause the increase of the NW lengths up to several micrometers. The long-chain amine mixture of oleylamine and 1-dodecylamine acts as reaction medium and ligands (or surfactants) to control the sizes of Ag 2 Se seeds and ZnSe NWs within several nanometers (the mean diameter of NWs: ∼5.5 nm). The microstructure studies by HRTEM reveal the presence of zinc blende (ZB)/wurtzite (W) alternations and a number of stacking faults and twins within individual ZnSe ultrathin NWs. These NWs exhibit optical quantum confinement effect due to the diameters smaller than the theoretical exciton Bohr diameter of bulk ZnSe. Raman spectrum and photoelectronic performance under white light illumination are also presented.
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