Figure 1 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
SEM and TEM images and I-V characteristic curves of the isolated CdS microrope. (a) SEM image of an isolated CdS microrope and a pair of Pt microleads fabricated with focused ion beam deposition. The inset shows the TEM image of the CdS microrope, which is composed of twisted CdS nanowires. (b) I-V characteristic curves of the isolated CdS microrope at different temperatures from 360 down to 60 K; the curves are symmetric.
Source publication
CdS is one of the important II-VI group semiconductors. In this paper, the electrical transport behavior of an individual CdS microrope composed of twisted nanowires is studied. It is found that the current-voltage (I-V) characteristics show two distinct power law regions from 360 down to 60 K. Space-charge-limited current (SCLC) theory is used to...
Similar publications
In this work, the stability, mechanical properties, mechanical anisotropy properties, electronic properties and effective mass anisotropy of C2/m-20 Si1-xGex (x = 0, 0.2, 0.4, 0.6, 0.8, 1) are studied through ab initio calculations. Effective mass is an important index to measure the transport properties of semiconductor. The analysis of effective...
Single wall carbon nanotubes (SWNT) have been a significant research topic as active layers for thin film transistors (TFTs) due to their high charge carrier mobility beyond that of crystalline silicon. In this study, we report an effective approach to achieve a very high field-effect mobility and on/off ratio for solution processed semiconducting...
High quality single crystals of WTe$_2$ were grown using a Te flux followed
by a cleaning step involving self-vapor transport. The method is reproducible
and yields consistently higher quality single crystals than are typically
obtained via halide assisted vapor transport methods. Magnetoresistance
(MR)values at 9 Tesla and 2 Kelvin as high as 1.75...
Spin-gapless semiconductors (SGSs), the new generation of spintronic materials, have received increasing attention recently owing to their various attractive properties such as fully spin-polarization and high carrier mobility. Based on their unique band structures, SGSs can be divided into two types, parabolic and Dirac-like linear. The linear-typ...
Carrier mobility (weighted mobility more specifically) of thermoelectrics fundamentally determines its power factor, representing a new cut‐in point to optimize the thermoelectric performance. However, researches on enhancing the carrier mobility to improve power factor has been overlooked. In present work, we highlight a significant mobility enhan...
Citations
... The observed OFF-state dependence can be interpreted as follows: In the low-voltage region from 0.02 to 0.14 V, electrons injected from Pt electrodes fill the trap and the device exhibits Ohmic-like conduction (I ∝ V) [21,22]. The increase of the exponent from V 1.32 to V 1.55 at higher voltages is related to trap state distribution under the conduction band, suggesting that the conduction mechanism of the HRS is consistent with classical space charge-limited current (SCLC) theory [23]. To see the role of the temperature on the power exponent of the voltage, we divide the voltage range into three regions. ...
... According to SCLC theory, the presence of traps can distort the shape of I−V curves from an ideal square law to much higher power dependence on voltage. For instance, I ∝ V 2 indicates that the device/material is in an ideal trap-free state and for exponents greater than 2, the material is in a trap state [23]. To show the temperature effects on the trap state of the device, we plotted in Fig. 5 the temperature dependencies of the exponents ( , , and ) that were extracted from the fitting shown in Fig. 2d. ...
The time-dependence of ON and OFF switching states in Pt/NiOx\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$_{x}$$\end{document}/Pt crossbar devices was measured between 300 K and 180 K. We find that the OFF-state resistance increases with time and this positive relaxation rate is reduced upon cooling, whereas the resistance decreases with time for the device in the ON state, and such negative relaxation rate increases with cooling and below 260 K, it becomes temperature independent. Furthermore, devices with a larger OFF/ON ratio and negligibly small relaxation rates at low temperatures may present great benefits for cryogenic memory applications. In this work, we discuss the mechanism behind these thermally and bias activated changes.
... This is consistent with the decrease in trap density and an increase in grain size, leading to less charge carrier scattering in the MAPb(I 1−x Br x ) 3 active layer as MABr thickness is increased. The calculated charge carrier mobility values are within the range for inorganic semiconductors (10 −4 − 10 3 cm 2 V −1 s −1 ) (Yu et al., 2015). However, they are two orders of magnitude lower than values of single crystals calculated using the SCLC method (Saidaminov et al., 2015;Herz, 2017;Chen et al., 2018). ...
Lead iodide (PbI 2 )-rich methylammonium lead bromide-iodide (MAPb(I 1– x Br x ) 3 ) thin-films were prepared by sequential physical vapor deposition of methylammonium lead tri-bromide (MAPbBr 3 ) on methylammonium lead tri-iodide (MAPbI 3 ) bottom layer. The structural, optical, morphological, and electrical properties of the thin-films were studied as the thickness of methylammonium bromide (MABr) was increased from 300 to 500 nm. X-ray diffractograms confirmed transformation of tetragonal MAPbI 3 ( x is 0.0) to the cubic-like structure of MAPbBr 3 ( x is 1.0) as MAPb(I 1– x Br x ) 3 ( x = 0.89–0.95) and PbI 2 were formed. The bromine mole ratio x decreased as MABr thickness increased. UV-Vis absorption spectra showed that the bandgap of the thin alloy film decreased from 2.21 to 2.14 eV as x decreased. Scanning electron micrographs depicted densely packed grains that entirely covered the substrate and contained very few pinholes. The average grain size increased from 150 to 320 nm as x decreased. Electrical properties showed high charge carrier mobility that increased linearly with MABr thickness. FTO/MAPb(I 1– x Br x ) 3 /Au devices using fluorine-doped tin oxide (FTO) as substrate and gold (Au) as contacts were fabricated and current-voltage characteristics were determined. Space-charge-limited current theory was applied to charge carrier mobility and trap density of MAPb(I 1– x Br x ) 3 thin-films. The charge carrier mobility increased as x decreased. The power conversion efficiency (PCE) of FTO/MAPbBr 3 /Au, FTO/MAPb(I 0.11 Br 0.89 ) 3 /Au and FTO/MAPbI 3 /Au solar cells were 0.56, 0.62, and 1.15%. Devices including titanium dioxide compact layer (c-TiO2) and titanium dioxide mesoporous (m-TiO 2 ) layer as electron transport layers were also fabricated for the application of Mott-Shottky (M-S) theory. Analyses of dark current-voltage and capacitance-voltage curves of FTO/c-TiO 2 /m-TiO 2 /MAPb(I 0.11 Br 0.89 ) 3 solar cells revealed a sizeable built-in voltage ( V bi ) of 1.6 V and an accumulation of charge at interfaces for voltages greater than 0.2 V, respectively. Similar analyses for FTO/TiO 2 /MAPbI 3 /Au showed a small V bi of 0.7 V and no charge carrier at interfaces. The work paves a way for reproducible growth of MAPb(I 1– x Br x ) 3 for solar cells and sheds more light on the degree of ion migration in mixed halide and pure halide perovskites.
... Our calculated μ p from 1.89 × 10 −2 to 1.08 × 10 −1 cm 2 V −1 s −1 for 400 and 500 nm MABr thick samples respectively. These values are within the range of μ p for inorganic semiconductors, 10 −4 -10 3 cm 2 V −1 s −1 [80]. However, they are two orders of magnitude lower than values of μ p for MAPbBr 3 single crystals obtained by the SCLC method. ...
Methylammonium lead tri-bromide (MAPbBr3) thin films were grown by sequential physical vapor deposition of lead(II)bromide and methylammonium bromide (MABr). X-ray diffractograms confirmed the cubic MAPbBr3 structure with Pm¯3 m space group. UV-Vis spectra revealed a red shift in absorption onset from 540 to 550 nm as the thickness of MABr increased with an optimum band gap of 2.28 eV, obtain from a Tauc Plot. Field emission scanning electron micrographs showed large pin-hole-free and densely packed grains with average grain size that increased from 217 to 302 nm with the thickness of MABr. Analysis of dark current-voltage characteristics of Au/MAPbBr3/FTO devices revealed ohmic behavior at low voltages and trap-limited space charge limited current at high voltages. The carrier mobility increased from 1.89 x 10-2 to 1.08 x 10-1 cm2 V−1 s−1 while trap density decreased from 1.89 x 1016 to 1.40 x 1016 cm-3 as the thickness of MABr increased.
... V t generally depends on the number of nanocrystals in the nanostructure, the capacitance of the conductive region, and the capacitance between each region and the back gate. This linear-nonlinear transition and the appearance of V t at low temperature could be attributed to the Coulomb blockade's limitation on the conductivity, and similar transitions are observed in nanowires [50] and nanotubes [51] of various complex compounds. The transition to the non-linear I-V curve shows the gradual nature of the Coulomb interstitial structure. ...
We systematically studied the structure, magnetism, resistance, magnetoresistance (MR) and nonlinear current-voltage (I-V) curves of La0.33Pr0.34Ca0.33MnO3 (LPCMO) nanofibers via electrospinning and followed calcination. Magnetic study shows that this nanosystem can form long-range order and generate spin-glass states at low temperatures. The resistance and MR studies indicate the presence of metal insulator transitions and colossal MR effects in the system, respectively. One-dimensional variable range hopping (1D VRH) model is used to explain the high-temperature segment behavior of resistance and MR. The behavior of the nonlinear I-V curves indicates the exist of threshold voltage and zero bias conductance at low temperatures in the LPCMO nanowires, which represents the existence of Coulomb gap.
... The case of α>2 can be understood in terms of a space-charge-limited current (SCLC) regime that is controlled by the trapped charge density. In this case, the conduction mechanism can be described based on several factors, such as the free carriers induced by impurities/ defects, the deep-trap energy level due to the oxygen vacancies, and the carriers injected from the electrodes [37,38]. ...
... The slopes of the HRS state I and II are α=4.28 ( ) µ I V 4.3 and 1.89 ( ) µ I V , 1.9 respectively, which can be regarded as α>1, related to the trap state distribution in the SCLC conduction mechanism [38]. When the negative voltage was applied, the trapped carriers began to be released and the current was increased. ...
... The higher the applied negative voltage, the more free carriers that were released. Therefore, it is possible to describe the I−V characteristics as being due to a process of charge trapping and de-trapping that is dominated by the SCLC mechanism [38]. Finally, the slopes of the LRS states (III and IV) in figure 3 ...
To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current−voltage (I −V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I−V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.
Nanowires have attracted widespread attention as a result of breakthroughs in nanotechnology due to their new features and potential applications. Lead selenide (PbSe) nanowires have acquired a lot of interest recently because of their exceptional performance and wide range of applications. Electrochemical deposition was used to create arranged PbSe nanowires in polycarbonate templates. Here, the effects of 120 MeV Au⁹⁺ swift heavy ion irradiationat fluence ranging from 1 × 10⁹ to 1 × 10¹² ions/cm² on the morphology, crystalline structure, optical and electrical properties were investigated. In the Ion Distribution and Quick Calculation of Damage mode, the TRIM (Transport of Ions in Matter) simulation was employed, and the damage was computed using quick statistical estimates based on the Kinchin-Pease formalism. The primitive and ion irradiated nanowires were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, UV-Visible spectroscopy and Current-Voltage characteristics. The results of Raman spectroscopy and X-ray diffraction imply that irradiated nanowires with minimal strain retain their crystallinity. The irradiation has shown strong impact on the optical constants like Optical band gap, Refractive index, high frequency and static dielectric constant and electron effective mass and optical band gap with no morphological change. At room temperature, the results of electrical properties studies for both primitive and irradiated nanowires are also provided. Our findings encourage the employment of nanowires in the futurefor photonic and electronic applications.
We study the effect of disorder and dephase in transmission of a CdS quantum wire using the Green’s function technique. Our results show that the transmission decreases with the increasing disorder strength. The resistance of a CdS quantum wire with phase-breaking scattering only increases with increasing dephasing. Obtained results show that the drain current of a CdS quantum wire with inelastic scattering by phonons with energy \(\hbar \omega = 30\) meV decreases with the increasing disorder strength. Moreover, our theoretical results are independently supported by simulations of CdS disordered quantum wires based on a tight-binding model.
Ag2S/Ag heteronanostructure has been produced by a simple one-stage chemical deposition from aqueous solutions of silver nitrate, sodium sulfide, and sodium citrate with the use of monochromatic light irradiation. For simultaneous synthesis of Ag2S and Ag nanoparticles, deposition has been performed from reaction mixtures with reduced sodium sulfide concentration. The size of Ag2S and Ag nanoparticles is 45–50 and 15–20 nm, respectively. It is established that in the contact layer between silver sulfide and silver, nonconducting α-Ag2S acanthite transforms into superionic β-Ag2S argentite under the action of external electric field. The scheme of the operation of a resistive switch based on an Ag2S/Ag heteronanostructure is proposed. The UV–Vis optical absorption spectra of colloidal solutions of Ag2S/Ag heteronanostructures have been studied.
Graphical Abstract
We present a theory for the description of morphology of semiconductor films with nanostructures and electrical conductivity of quantum nanowires. The theory is based on a conception of a fractal distribution of current carriers and impurities in semiconductors containing nanoclusters. Theoretical results qualitatively correspond to experimental data on morphology and electrical properties of silicon films with vertical nanowires.
