Doping dependent crystal structures and optoelectronic properties of n-type CdSe:Ga nanowries

Probing the photovoltaic properties of Ga-doped CdS–Cu2S core–shell heterostructured nanowire devices

In this study Ga-doped cadmium sulfide (CdS) nanowires (NWs) were grown through chemical vapor deposition.

Efficient Self-Driven Photodetectors Featuring a Mixed-Dimensional van der Waals Heterojunction Formed from a CdS Nanowire and a MoTe2 Flake

Heterojunctions formed from low-dimensional materials can result in photovoltaic and photodetection devices displaying exceptional physical properties and excellent performance. Herein, a mixed-dimensional van der Waals (vdW) heterojunction comprising a 1D n-type Ga-doped CdS nanowire and a 2D p-type MoTe₂ flake is demonstrated; the corresponding photovoltaic device exhibits an outstanding conversion efficiency of 15.01% under illumination with white light at 650 µW cm^-2 . A potential difference of 80 meV measured, using Kelvin probe force microscopy, at the CdS-MoTe₂ interface confirms the separation and accumulation of photoexcited carriers upon illumination. Moreover, the photodetection characteristics of the vdW heterojunction device at zero bias reveal a rapid response time (<50 ms) and a photoresponsivity that are linearly proportional to the power density of the light. Interestingly, the response of the vdW heterojunction device is negligible when illuminated at 580 nm; this exceptional behavior is presumably due to the rapid rate of recombination of the photoexcited carriers of MoTe₂ . Such mixed-dimensional vdW heterojunctions appear to be novel design elements for efficient photovoltaic and self-driven photodetection devices.

Guided CdSe Nanowires Parallelly Integrated into Fast Visible-Range Photodetectors

One-dimensional semiconductor nanostructures, such as nanowires (NWs), have attracted tremendous attention due to their unique properties and potential applications in nanoelectronics, nano-optoelectronics, and sensors. One of the challenges toward their integration into practical devices is their large-scale controlled assembly. Here, we report the guided growth of horizontal CdSe nanowires on five different planes of sapphire. The growth direction and crystallographic orientation are controlled by the epitaxial relationship with the substrate as well as by a graphoepitaxial effect of surface nanosteps and grooves. CdSe is a promising direct-bandgap II-VI semiconductor active in the visible range, with potential applications in optoelectronics. The guided CdSe nanowires were found to have a wurtzite single-crystal structure. Field-effect transistors and photodetectors were fabricated to examine the nanowire electronic and optoelectronic properties, respectively. The latter exhibited the fastest rise and fall times ever reported for CdSe nanostructures as well as a relatively high gain, both features being essential for optoelectronic applications.

Thermal conductivity of zinc blende and wurtzite CdSe nanostructures

Many binary octet compounds including CdSe can be grown in either the wurtzite (WZ) or zinc blende (ZB) phase, which has aroused great interest among the research community in understanding the phase dependence of the thermal transport properties of these compounds. So far, it has been debatable whether the ZB phase possesses higher thermal conductivity than the WZ phase. In this work, we report on thermal conductivity measurements of CdSe nanowires/nanoribbons with both WZ and ZB phases via a suspended device method. At room temperature, the thermal conductivity of all the ZB CdSe nanostructures measured in this work is higher than the bulk thermal conductivity of the WZ CdSe reported in the literature, suggesting that the bulk thermal conductivity of the ZB CdSe is higher than that of the WZ phase. Our result is different from previous experimental results in the literature for InAs nanowires which suggest similar thermal conductivity values for the bulk ZB and WZ InAs crystals. The higher thermal conductivity of the ZB CdSe can be explained by its lower anharmonicity and a smaller number of atoms per unit cell compared to the WZ phase.

Tunable p-type doping of Si nanostructures for near infrared light photodetector application

A near infrared light nano-heterojunction photodetector was fabricated by combining graphene and boron doped p-type silicon nanowires, which were synthesized by a co-thermal evaporation method.

Fabrication of p-type ZnSe:Sb nanowires for high-performance ultraviolet light photodetector application

p-type ZnSe nanowires (NWs) with tunable electrical conductivity were fabricated on a large scale by evaporating a mixed powder composed of ZnSe and Sb in different ratios. According to the structural characterization, the Sb-doped ZnSe NWs are of single crystalline form and grow along the [001] direction. The presence of Sb in the ZnSe NWs was confirmed by XPS spectra. Electrical measurement of a single ZnSe:Sb NW based back-gate metal-oxide field-effect-transistor reveals that all the doped NWs exhibit typical p-type conduction characteristics, and the conductivity can be tuned over eight orders of magnitude, from 6.36 × 10(-7) S cm(-1) for the undoped sample to ∼37.33 S cm(-1) for the heavily doped sample. A crossed p-n nano-heterojunction photodetector made from the as-doped nanostructures displays pronounced rectification behavior, with a rectification ratio as high as 10(3) at ±5 V. Remarkably, it exhibits high sensitivity to ultraviolet light illumination with good reproducibility and quick photoresponse. Finally, the work mechanism of such a p-n junction based photodetector was elucidated. The generality of the above result suggests that the as-doped p-type ZnSe NWs will find wide application in future optoelectronics devices.

Nonvolatile multibit Schottky memory based on single n-type Ga doped CdSe nanowires

Nonvolatile resistive switching has been observed for the first time in CdSe nanowire (NW)/Au Schottky barrier diodes, where a Schottky contact electrode and an Ohmic contact electrode were formed at the Au/CdSe NW and CdSe NW/In interfaces, respectively. The CdSe NWs Schottky devices were found to possess multibit storage ability in an individual nanowire, and exhibited excellent memory characteristics, with a resistance on/off ratio exceeding four orders of magnitude, a long retention time of over 10(4) s and a lower operating voltage of 2 V. By replacing the SiO(2)/Si substrate with a poly ethylene terephthalate substrate, flexible and transparent memory devices with superior stability under strain were realized. The resistive switching of CdSe NW/Au Schottky devices is understood by electron trapping and detrapping in the interfacial oxide layer. Our findings provide a viable way to create new functional high-density nonvolatile multibit memory devices compatible with simple processing techniques for normal one-dimensional nanomaterials.