Catalyst- and template-free low-temperature in situ growth of n-type CdS nanowire on p-type CdTe film and p-n heterojunction properties

Abstract

CdS is an important semiconductor used in optoelectronic devices. Simple techniques for growing CdS nanostructures are thus essential at a low cost. This study presents a novel method for growing singlecrystal n-type CdS nanowires on p-type CdTe films by thermal annealing in an H 2 S/N 2 mixed gas flow, which does not require the help of a catalyst or template. The formation process and growth mechanism of the nanowires are investigated. Well-dispersed whiskerlike CdS nanostructures are obtained at an appropriate annealing temperature and duration. We suggest that the stress-driving mechanism of nanowire formation may contribute to the growth of CdS nanowires, and that the evaporation of Te through the boundaries of the CdS grain seeds plays an important role in the sustainable growth of nanowire. In addition, CdS/CdTe heterojunction device is fabricated on Mo glass. The I-V characteristic of the heterojunction in dark shows typical rectifying diode behavior. The turn-on voltage can be regulated by annealing conditions. Meanwhile, the obvious photovoltaic effect is obtained on the in situ growth heterojunction prepared at low annealing temperature. Hence, this is a new fabricated method for CdTe-based materials in the field of energy conversion.CdS is a well-studied semiconductor with versatile properties, such as a direct band gap of 2.4 eV at room temperature, a high refractive index, excellent transport properties and good chemical and thermal stability. It has been used extensively in photovoltaic devices, light-emitting diodes in flat panel displays, transistors, and logic gates 1-3 . Low-dimensional CdS nanostructures, such as nanorods, nanowires, and nanotubes, have attracted increasing attention because of their superior optical, physical, electronic and catalytic properties compared with traditional thin film and bulk materials [4][5][6] . A wide range of applications for nanodevices and nanosystems based on these CdS nanostructures has recently been explored, including a thin film transistor fabricated on CdS nanoribbons 4 , and chemical vapor deposition (CVD) [15][16][17] . Although each of these methods has its own advantages, most involve a solution process or organic solvents 13,18 , and the reaction process is uncontrollable. The CVD method is known to be effective in the large-scale fabrication of CdS nanostructures. However, due to the high sublimation temperature of CdS powder, the growth temperature of CdS nanostructures is as high as 800 °C 12,19 , and the growth process requires the use of an Au catalyst 20 . Unfortunately, Au functions as an impurity, trapping electrons and holes in the nanostructure, and affecting the performance of the device. Templates, such as anodic aluminum oxide 9,21 , which are used to prepare nanowires, can also yield better CdS arrays. However, this method also needs Au catalyst to grow nanostructure 9 . So, an effective method

Synthesis of mesoporous networks of metal-chalcogenide nanocrystals for photocatalytic applications and hydrogen fuel production

“…e., 1.2 eV) and their ~2:1 area ratio, match well the respective values reported for S2-ions in CdS [500,501]. The lack of further S 2p3/2 and S 2p1/2 peak splitting suggests that there are no S lattice atoms bonding with Ni, since the S 2p3/2 and S 2p1/2 XPS peaks of NiS are close to 161.9 eV and 162.8 eV, respectively, thereby indicating that there is no contribution of a NiS phase in the composite Ni-CdS heterostructures [361,390].…”

Dielectric and Conductivity Relaxation of rGO@CdS Nanocomposites via In Situ Assembly of CdS Nanoparticles on an rGO Layer

“…Under certain temperature and alkaline environment, the degree of GO reduced is inversely related to the amount of GO added. In addition, specific vibration modes centered at 302, 603, and 907 cm –1 were observed in CdS and rGO@CdS nanocomposites, matching with the vibration modes of LO, 2LO, and 3LO modes of the CdS, respectively . The vibration mode of LO was enlarged between 200 and 400 cm –1 (the inset in Figure ).…”

“…In addition, specific vibration modes centered at 302, 603, and 907 cm −1 were observed in CdS and rGO@CdS nanocomposites, matching with the vibration modes of LO, 2LO, and 3LO modes of the CdS, respectively. 28 The vibration mode of LO was enlarged between 200 and 400 cm −1 (the inset in Figure 7). The intensity of LO vibration mode gradually weakens and the Raman shift significantly blue shifts with the addition of GO, which means that the size of CdS nanoparticles decreases, which is consistent with the results of XRD and TEM analysis.…”

“…65-3414, while that located at 31.7 o is related to the orthorhombic structure of CdS according to JCPDS card No. 43-0985. , In addition, the diffraction peaks at 18 and 29.6 o belong to the monoclinic structure of S according to JCPDS card No. 34-0941.…”

“…43-0985. 28,29 In addition, the diffraction peaks at 18 and 29.6 o belong to the monoclinic structure of S according to JCPDS card No. 34-0941.…”