No abstract

Composites (or complex materials) are formed from two or many constituent materials with novel physical or chemical characteristics when integrated.

possessing high photocurrent gain, fast response speed, high photosensitivity, wide response wavelength, and multiband photodetection are highly desired. [1][2][3][4] For this purpose, nanowires with large surface-to-volume ratio and quantum confinement effect show huge advantages over the bulk and thin film counterparts for fabrication of high performance photodetectors. [5][6][7][8][9][10] Since the discovery of carbon nanotubes, there are many reports about the photodetectors based on various 1D inorganic semiconductor nanostructures. For example, Si, Ge, ZnO, Ga 2 O 3 , CdS, ZnSe, CdSe, GaN, GaAs, InAs, CsPbBr 3 , and CsPb 2 Br 5 nanowires/nanobelts were used to fabricate photodetectors and demonstrate excellent photoresponse properties. [11][12][13][14][15][16] However, it is still very challenging to obtain the broad spectral response and high responsivity in these single component nanowire photodetectors due to the constraint of bandgap engineering, light absorptivity, and photogenerated carriers transfer efficiency. [17,18] High-quality semiconductor heterostructure nanowires (HNWs) integration with multicomponent can increase the absorption ability and extend the photoresponse range effectively. Actually, CdS/CdS x Se 1−x axial heterostructure nanowire photodetectors have shown more superior photodetection properties than that of single component CdS or CdS x Se 1−x . However, the controllable synthesis of axial HNWs is elusive and there are only few reports to date. [19,20] Different from the recent CdS/CdS x Se 1−x axial HNWs, which contain heavy-metal Cd element and might be unfavorable for practical application. ZnSe and ZnS with direct bandgap of 2.7 and 3.6 eV at room temperature are promising semiconductor materials for optoelectronics application in the visible and ultraviolet region. [21][22][23] Compared to binary ZnSe and ZnS nanowires, the recent synthesis and optical properties characterization of ZnS x Se 1−x ternary alloy nanostructures demonstrate tunable bandgap and photoluminescence (PL) properties, [24,25] which are similar to CdS x Se 1−x . These results favor the synthesis of ZnS x Se 1−x /ZnSe HNWs that is more friendly to environment and human health. However, to the best of our knowledge, there is not any report about the ZnSe x S 1−x /ZnSe axial heterostructure due to the phase structure, lattice mismatch, and the melting point between ZnSe and ZnS, which makes the epitaxial growth of ZnSe along the Semiconductor heterostructure nanowires (HNWs) are excellent candidates for application in compact optoelectronics devices with high performance due to the heterojunction interface effect. However, the controllable fabrication of high-quality nano-heterostructures is elusive. In this paper, the controllable growth and optoelectronics device application of high-quality ZnS 0.49 Se 0.51 / ZnSe axial HNWs are reported. The as-synthesized HNWs are straight with uniform diameter distribution of 50-100 nm. Microstructural characterization reveals single crystal and abrupt heterojunction int...

Graphene-based optical sensing devices have been widely studied for their broad band absorption, high carrier mobility, and mechanical flexibility. Due to graphene’s weak light absorption, studies on graphene-based optical sensing thus far have focused on hybrid heterostructure devices to enhance photo-absorption. Such hybrid devices need a complicated integration process and lead to deteriorating carrier mobility as a result of heterogeneous interfaces. Rippled or wrinkled graphene has been studied in electronic and optoelectronic devices. However, concrete demonstrations of the impact of the morphology of nanofilms (e.g., graphite and graphene) associated with light absorption in optical sensing devices have not been fully examined. This study explored the optical sensing potential of a graphite nanofilm surface with ripples induced by a stretchable polydimethylsiloxane (PDMS) supporting layer under different stretch:release ratios and then transferred onto silicon, both under experimental conditions and via simulation. The optical sensing potential of the rippled graphite nanofilm was significantly enhanced (260 mA/W at the stretch–release state of 30%), as compared to the pristine graphite/PDMS (20 mA/W at the stretch–release state of 0%) under laser illumination at a wavelength of 532 nm. In addition, the results of our simulated computation also confirmed the improved light absorption of rippled graphite nanofilm surface-based optical sensing devices, which was comparable with the results found in the experiment.