P-type Semiconductor Characteristics Research Articles

Preparation and Performance Research of CuInSe<sub>2</sub> Materials Applied in Solar Cell

At present, CuInSe2 (referred to as CIS) semiconductor has become one of the hot points in solar cell field at home and abroad for its excellent performances, such as direct bandgap, high light absorption coefficient, high photoelectric conversion efficiency and long-term stability. In this paper, the CIS bulk materials are prepared by the horizontal Bridgman method with double-heat sources, the crystal structure, microstructure morphology and composition of the samples are analyzed in X-ray diffraction instrument (XRD) and scanning electronic microscope (SEM) with Energy Dispersive X-ray Spectrum (EDX), and surface electrical state and electrical properties of the samples are characterized in X-ray photoelectron spectroscopy (XPS) and four point resistivity test system. The results show that the CIS crystal was grown, and that the conductive performance of the samples is good which display the characteristics of p-type semiconductor. Furthermore, a thin film CIS sample was obtained by argon ion-beam scanning bombardment, and it has high solar energy absorptivity and the bandgap of 0.99 eV analyzed in Ultraviolet-visible Spectrum that is suitable for solar cell. Keywords: Solar

Syntheses, structures and photoelectronic properties of a series of tri- and tetra-nuclear metal complexes based on a 36-membered tetraphenol macrocyclic ligand

In this article, tetranuclear Zn II coordination complexes [Zn 4L(μ 2-OH) 2]·2(NO 3)·6(CH 3OH)·H 2O ( 1) and [Zn 4L(μ 2-OH) 2(H 2O) 2]·( p-bdc)·2(CH 3OH)·3H 2O ( 2), dinuclear Zn II complex [Zn 4L(NH 2-bdc) 2]·2(CH 3OH)·3H 2O ( 3), and trinuclear Cd II complexes [Cd 3L( m-bdc)]·6.5H 2O ( 4) and [Cd 3L(NH 2-bdc)]·5.5H 2O ( 5), based on a tetraphenol 36-membered macrocycle (L) having four ethylenediamine and four 2,6-diformyl-4-methylphenol functionalities, have been synthesized at room temperature ( p-bdc = 1,4-benzenedicarboxylate, NH 2-bdc = 5-aminoisophthalate and m-bdc = 1,3-benzenedicarboxylate). In 1 and 2, four Zn II centers are bridged by phenoxide and hydroxy atoms of the L ligands to form tetranuclear Zn II complexes. The inorganic and organic anions in 1 and 2 do not coordinate to Zn II centers, but act as counter anions. In 3, two Zn II centers are bridged by two phenoxide O atoms to form a Zn II cluster (Zn 2O 2N 4). Moreover, two (Zn 2O 2N 4) clusters within the ring of the L ligand are further bridged by two NH 2-bdc anions in a monodentate fashion. Compound 4 possesses the trinuclear Cd II clusters (Cd 3N 8O 8), which has a similar structure to compound 5. The trinuclear Cd II clusters are bridged by the dicarboxylate anions to yield an infinite coordination polymers chain. The photoelectric transfer properties of complexes 1, 2 and 4 were investigated by surface photovoltage spectroscopy (SPS) and the field-induced surface photovoltage spectra (FISPS) techniques. The results reveal that the complexes exhibit positive surface photovoltage (SPV) responses in the range of 300–600 nm, possessing the p-type semiconductor characteristics. So far, the surface photovoltage properties of the macrocycle complexes based on tetraphenol macrocyclic ligands were investigated for the first time. Moreover, elemental analyses, IR spectra, and luminescent properties of these compounds were also studied.

Rh-Doped SrTiO3 Photocatalyst Electrode Showing Cathodic Photocurrent for Water Splitting under Visible-Light Irradiation

A Rh-doped SrTiO(3) (SrTiO(3):Rh) photocatalyst electrode that was readily prepared by pasting SrTiO(3):Rh powder onto a transparent indium tin oxide electrode gave a cathodic photocurrent under visible-light irradiation (λ > 420 nm), indicating that the SrTiO(3):Rh photocatalyst electrode possessed p-type semiconductor character. The cathodic photocurrent increased with an increase in the amount of doped Rh up to 7 atom %. The incident-photon-to-current efficiency at 420 nm was 0.18% under an applied potential of -0.7 V vs Ag/AgCl for the SrTiO(3):Rh(7 atom %) photocatalyst electrode. The photocurrent was confirmed to be due to water splitting by analyzing the evolved H(2) and O(2). The water splitting proceeded with the application of an external bias smaller than 1.23 V versus a Pt counter electrode under visible-light irradiation and also using a solar simulator, suggesting that solar energy conversion should be possible with the present photoelectrochemical water splitting.

Organic electrochemical transistors based on a dielectrophoretically aligned nanowire array

In this study, we synthesized an organic electrochemical transistor (OECT) using dielectrophoresis of a carbon nanotube-Nafion (CNT-Nafion) suspension. Dielectrophoretically aligned nanowires formed a one-dimensional submicron bundle between triangular electrodes. The CNT-Nafion composite nanowire bundles showed p-type semiconductor characteristics. The drain-source current decreased with increasing gate voltage. The nanowire bundles showed potential as pH sensor because the drain-source current ratio varied linearly according to the gate voltage in pH buffers.

P-Type and n-type Cu 2O semiconductor thin films: Controllable preparation by simple solvothermal method and photoelectrochemical properties

p-Type and n-type Cu 2O thin films were controllably prepared using a simple solvothermal method by adjusting pH value of the copper (II) acetate aqueous solution. Photoelectrochemical experiments show that the Cu 2O thin films synthesized in acid and alkaline (or neutral) media present n-type and p-type semiconductor character, respectively. Moreover, the films prepared at pH 5 have the best photoelectrochemical properties. The mechanism for the formation of these p-type and n-type Cu 2O films is discussed. The Cu 2O p–n homojunction fabricated in this study shows typical p–n junction character. This facile preparation method may be a promising way to prepare p–n homojunctions for semiconductor devices.

Band Gap Opening of Bilayer Graphene by F4-TCNQ Molecular Doping and Externally Applied Electric Field

The band gap opening of bilayer graphene with one side surface adsorption of F4-TCNQ is reported. F4-TCNQ doped bilayer graphene shows p-type semiconductor characteristics. With a F4-TCNQ concentration of 1.3 x 10(-10) mol/cm(2), the charge transfer between each F4-TCNQ molecule and graphene is 0.45e, and the built-in electric field, E(bi), between the graphene layers could reach 0.070 V/A. The charge transfer and band gap opening of the F4-TCNQ-doped graphene can be further modulated by an externally applied electric field (E(ext)). At 0.077 V/A, the gap opening at the Dirac point (K), DeltaE(K) = 306 meV, and the band gap, E(g) = 253 meV, are around 71% and 49% larger than those of the pristine bilayer under the same E(ext).

Oriented-aggregation of organic organization: Morphology-controllable synthesis, surface photovoltage spectroscopy and morphology-dependent optical property

Assembled ZnQ 2·2H 2O microstructures, such as microsheet, sandwich-like structure and hexangular microflake, have been successfully prepared in CTAB microemulsion system through the stacking of ZnQ 2·2H 2O molecules and oriented aggregation of ZnQ 2·2H 2O original building blocks. Controlled experiments demonstrated that the morphologies of building block and final product could be readily tuned by reaction parameters, and a formation mechanism, involving re-precipitation, growth and oriented aggregation process, has been proposed on the basis of time-dependent experimental results. The obtained products were carefully characterized by X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscope (TEM), field-emission scanning electron microscope (FESEM), FT-IR spectrum, UV–vis spectrum and photoluminescence (PL) spectrum. The surface photovoltage (SPV) of the obtained ZnQ 2·2H 2O microstructures was investigated by means of surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (FISPS). The SPS and FISPS revealed that the photogenerated charges of ZnQ 2·2H 2O could be separated distinctly and ZnQ 2·2H 2O possessed p-type semiconductor characteristics, respectively. Furthermore, UV–vis and PL spectra evidenced the optical properties of ZnQ 2·2H 2O were sensitive to its microstructure or morphology.

Three Synthetic Routes to Single-Crystalline PbS Nanowires with Controlled Growth Direction and Their Electrical Transport Properties

Single-crystalline rock-salt PbS nanowires (NWs) were synthesized using three different routes; the solvothermal, chemical vapor transport, and gas-phase substitution reaction of pregrown CdS NWs. They were uniformly grown with the [100] or [110], [112] direction in a controlled manner. In the solvothermal growth, the oriented attachment of the octylamine (OA) ligands enables the NWs to be produced with a controlled morphology and growth direction. As the concentration of OA increases, the growth direction evolves from the [100] to the higher surface-energy [110] and [112] directions under the more thermodynamically controlled growth conditions. In the synthesis involving chemical vapor transport and the substitution reaction, the use of a lower growth temperature causes the higher surface-energy growth direction to change from [100] to [110]. The high-resolution X-ray diffraction pattern and X-ray photoelectron spectroscopy results revealed that a thinner oxide-layer was produced on the surface of the PbS NWs by the substitution reaction. We fabricated field effect transistors using single PbS NW, which showed intrinsic p-type semiconductor characteristics for all three routes. For the PbS NW with a thinner oxide layer, the carrier mobility was measured to be as high as 10 cm(2) V(-1) s(-1).

Three Synthesis Routes of Single-crystalline PbS Nanowires and Their Electrical Transport Properties

AbstractSingle-crystalline rock-salt PbS nanowires (NWs) were synthesized using three different routes; the solvothermal, chemical vapor transport, and gas-phase substitution reaction of pre-grown CdS NWs. They were uniformly grown with the [100] or [110], [112] direction in a controlled manner. In the solvothermal growth, the oriented attachment of the octylamine (OA) ligands enables the NWs to be produced with a controlled morphology and growth direction. As the concentration of OA increases, the growth direction evolves from the [100] to the higher surface-energy [110] and [112] directions. In the synthesis involving chemical vapor transport and the substitution reaction, the use of a lower growth temperature causes the higher surface-energy growth direction to change from [100] to [110]. We fabricated field effect transistors using single PbS NW, which showed intrinsic p-type semiconductor characteristics for all three routes. For the PbS NW with a thinner oxide layer, the carrier mobility was measured to be as high as 10 cm2V−1s−1.

Room temperature ozone sensing properties of p-type CuCrO 2 nanocrystals

Delafossite-type oxide CuCrO 2 nanocrystals and microcrystals were synthesized by hydrothermal and sol–gel method, respectively, and ozone sensors were prepared by deposition of the solution containing CuCrO 2 samples. At room temperature, the sensors resistance decreased upon exposure to 50–200 ppm ozone. This can be explained by the gas sensing characteristics of p-type oxide semiconductor. We also compared the response features of CuCrO 2 nanocrystals with CuCrO 2 microcrystals, and CuCrO 2 nanocrystals gave rise to better response features than CuCrO 2 microcrystals.

Ag8SiTe6: A New Thermoelectric Material with Low Thermal Conductivity

Here, we introduce a new thermoelectric material: Ag8SiTe6. Ag8SiTe6 indicated p-type semiconductor characteristics. The crystal structure of Ag8SiTe6 was quite complicated, which led to a very low thermal conductivity of 0.23 W m-1 K-1 at room temperature. A relatively high thermoelectric figure of merit of 0.48 was obtained at 800 K, which was mainly due to the very low thermal conductivity.

First-Principles Calculation of Electronic Structure and Optical Properties of Sb-Doped ZnO

The geometric structure, electronic structure, optical properties and the formation energy of Sb-doped ZnO with the wurtzite structure are investigated using the first-principles ultra-soft pseudo-potential approach of plane wave based upon the density functional theory. The calculated results indicate that the volume of ZnO doped with Sb becomes larger, and the doping system yields the lowest formation energy of Sb on the interstitial site and the oxygen site. Furthermore, Sb dopant first occupies the octahedral oxygen sites of the wurtzite structure. It is found that Sb substituting on oxygen site behaves as a deep acceptor and shows the p-type degenerate semiconductor character. After doping, the electron density difference demonstrates the considerable electron charge density redistribution, which induces the effect of Sb-doped ZnO to increase the charge overlap between atoms. The density of states move towards lower energy and the optical band gap is broadened. Our calculated results are in agreement with other experimental results and could make more precise monitoring and controlling possible during the growth of ZnO p-type materials.

Transformation of ZnTe nanowires to CdTe nanowires through the formation of ZnCdTe–CdTe core–shell structure by vapor transport

Single-crystalline ZnTe nanowires were transformed into single-crystalline CdTe nanowires by Cd vapor transport. The composition was controlled by adjusting the reaction time, and the formation of the ZnCdTe–CdTe core–shell nanocable structure as an intermediate was observed. Their morphology and crystal structure were retained during the transformation. The progressive composition change from ZnTe to CdTe tunes the emission wavelength from the green (528 nm) to red (855 nm) color regions . We fabricated field effect transistors using the ZnTe and CdTe nanowires, providing evidence that their p-type semiconductor characteristics remain the same after the transformation.

High-mobility transistors based on nanoassembled carbon nanotube semiconducting layer and SiO2 nanoparticle dielectric layer

The authors report the fabrication and characterization of high-mobility thin-film transistors (TFTs) using layer-by-layer (LBL) nano self-assembled single-walled carbon nanotubes (SWCNTs) as the semiconducting material and SiO2 nanoparticles as the gate dielectric material. The channel length and the effective thickness of the SWCNT semiconductor layer are 50μm and 38nm, respectively. The effective thickness of the SiO2 dielectric layer is 180nm. The SWCNT TFT exhibits p-type semiconductor characteristics and operates in the accumulation mode, with a hole mobility (μp) of 168.5cm2∕Vs, a normalized transconductance (gm∕W) of 0.5S∕m, a threshold voltage (Vth) of −3V, and an on/off current ratio (Ion∕off) of 4.2. The combination technique with LBL nano self-assembly and microlithography provides a simple, low-temperature, and highly efficient approach to fabricate inexpensive TFT devices.

Coherent Transport of Hole and Coulomb Blockade Phenomenon in Long p-Type Semiconductor Carbon Nanotube

We have succeeded in observing the coexistence of the Coulomb charging effect and the coherent transport of the hole in a single-walled carbon nanotube (SWNT) with a length of 4.5 µm at 8.6 K. SWNT channel field-effect transistor (FET) structures were prepared with two different channel lengths of 4.5 and 1.4 µm. The samples showed p-type semiconductor characteristics under large gate and drain biases at 8.6 K. At 8.6 K, on the other hand, single-hole transistor characteristics with different Coulomb charging energies corresponding to the length of the channel were observed in each sample. Drain current peaks with different periods corresponding to the length of the channel were also observed outside of the Coulomb blockade area for the higher drain voltages in each sample. The drain current peaks are attributed to resonant tunneling of the hole through the separation of the quantum energy levels originating from coherent transport of the hole in the entire semiconductive SWNT.

The fabrication and characterization of ZnO UV detector

ZnO films were deposited on GaAs substrates by radio frequency (rf) magnetron sputtering followed by an ambient-controlled heat treatment process for arsenic doping. In Hall measurements, the As-doped ZnO films showed the characteristics of p-type semiconductor. The ZnO thin film p–n homojuctions were then fabricated to investigate the electrical properties of the films. The p–n homojunctions exhibited the distinct rectifying current–voltage ( I– V) characteristics. The turn-on voltage was measured to be ~3.0 V under the forward bias. When ultraviolet (UV) light (λ = 325 nm) was irradiated on the p–n homojunction, photocurrent of ~2 mA was detected. Based on these results, it is proposed that the p–n homojunction herein is a potential candidate for UV photodetector and optical devices.

Solvent induced semiconductor type conversion of MEH-PPV investigated by surface photovoltage spectra

Organic solvents play an important role in determining the type of MEH-PPV based electronic devices. In this article, with the help of the external electric field induced surface photovoltage spectra, we present evidence that MEH-PPV in aromatic solvents, such as chlorobenzene and xylene, show p-type semiconductor characteristics and n-type semiconductor characteristics in nonaromatic solvents, such as tetrahydrofuran and chloroform, due to their different conformation.

Solvent induced semiconductor type conversion of MEH-PPV investigated by surface photovoltage spectra

Organic solvents play an important role in determining the type of MEH-PPV based electronic devices. In this article, with the help of the external electric field induced surface photovoltage spectra, we present evidence that MEH-PPV in aromatic solvents, such as chlorobenzene and xylene, show p-type semiconductor characteristics and n-type semiconductor characteristics in nonaromatic solvents, such as tetrahydrofuran and chloroform, due to their different conformation.

Interaction of methane with carbon nanotube thin films: role of defects and oxygen adsorption

This paper deals with the dependence of the electrical conductance on the presence of structural defects and of molecular oxygen adsorbates in carbon nanotube (CNT) thin films for gas molecule detection. Our results show that oxygen contamination may be responsible for the reported sensitivity of the electronic and transport properties to methane at room temperature. In particular, the sample exhibits a crossover from decreasing to increasing electrical resistance vs. methane concentration depending on the surrounding atmosphere. The obtained results show that when the nanotube walls contain topological defects, oxygen molecules become chemisorbed. We suggest that the conductivity type of the CNT can be changed from p-type to n-type by adsorption of O 2 acting as an electron and donor doping the CNTs, which has p-type semiconductor character in the outgassed state. The obtained results demonstrate that nanotubes could be used as sensitive chemical gas sensor likewise indicate that intrinsic properties measured on as-grown nanotubes may be severely changed by extrinsic oxidative treatments.

Thermoelectric Properties of Tl9BiTe6.

AbstractFor Abstract see ChemInform Abstract in Full Text.