P-type Semiconductor Characteristics Research Articles

Effects of pH and Cl− Content on Degradation Process of Pre-Passivated Stainless Steels in an Alkaline Solution

The degradation behavior of four prepassivated stainless steels (SSs) in the alkaline solutions with different Cl− concentrations and pH values were investigated by cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis and the X-ray photoelectron spectroscopy (XPS). The results indicated that the pH value and Cl− concentration, together with the phase ratio difference in the microstructure of SS, played a critical role in the degradation process of passive film. At low pH and high Cl− concentration, the passive film gradually enriched in Fe3+ and Cr3+ species and depleted in Fe2+ oxides and its self-regeneration process became more difficult. As the pH decreased, the passive film exhibited clear n-type and p-type semiconductor characteristics more clearly, and the decrease in dopant density well reflected the changes in Fe2+/Fe3+ ratio and electrochemical behavior. Based on the viewpoint of adsorption balance between OH− with inhibitory effect and Cl− with promotion effect on the degradation process, a mechanism for the degradation process of prepassivation film was proposed.

Effects of Sn dopant on power factor of Tl8.67Sb1.33-xSnxTe6 nanoparticles

In this research work the thermoelectric and electrical performance of Sn doped Tellurium Telluride Tl8.67SnxSb1.33-xTe6 (x=0.61, 0.63, 0.65, 0.67, 0.68, 0.70), was studied. The samples were synthesized by melting method. By XRD and EDX analysis it has been confirmed that single phase tetragonal crystal structure with no any other impurities. The See beck co-efficient (thermo power) (S) shows increasing positive trend showing p-type semiconductor characteristics with whole temperature range from 300 to 550 K. At ambient temperature complex behavior of See beck coefficient for Sn doped compounds has been observed initially S decreasing with increase in Sn concentration i.e. x=0.65, and then S increases with increase in Sn contents up to x=0.70. In additional the electrical conductivity (σ) and the power factors have also shows the same complex behavior with the increase of Sn concentrations.. Telluride’s are narrow band-gap semiconductors, with all elements in common oxidation states, according to (Tl+ )9(Sb3+) (Te2- )6.It is found that the power factor is increases with Sn concentrations as well as increase in temperature range from 300-500 K.

First-Principles Calculations of the Structural, Electronic and Optical Properties of Yttrium-Doped SnO2

Abstract We use FP-LAPW method to study structural, electronic, and optical properties of the pure and Y-doped SnO2. The results show that by Y doping of SnO2 the band gaps are broadened, and still direct at Γ-point. For pure SnO2 material, the obtained values of the direct band gap are 0.607 eV for GGA-PBE and 2.524 eV for GGATB-mBJ, respectively. This later is in good agreement with the experimental data and other theoretical results. The Fermi level shifts into the valence band and exhibits p-type semiconductor character owing mainly from the orbital 4d-Y. Additionally, the calculated optical properties reveal that all concentrations are characterized by low reflectivity and absorption via wavelength λ (nm) in the visible light and near-infrared (NIR) ranges, which leads to a redshift in the optical transparency.

Electronic property of intrinsic point defect system on β–Si3N4(0001) surface

The intrinsic point defect influence data for [Formula: see text]–Si3N4by far are incomplete and experimental clarification is not easy. In this contribution, the effects of vacancy ([Formula: see text], [Formula: see text] and [Formula: see text]) and interstitial ([Formula: see text] and [Formula: see text]) defects on the electronic properties of H-passivated [Formula: see text]–Si3N4(0001) surface are explored based on density functional theory (DFT) calculation. The results show that it is easier to form [Formula: see text] vacancy defects in the surface layer under Si-rich conditions. The existence of N vacancies makes the bottom of conduction bands shift downwards, and the top of valance band is away from Fermi level. The presence of [Formula: see text] makes the system have the characteristics of p-type semiconductor, and the closer to the inner layer, the narrower the range of additional energy bands and the greater the degree of localization of electrons. The closer the Si atom vacancy is to the surface, the smaller the photon energy corresponding to the maximum absorption coefficient is. Compared with the N vacancy system, the Si vacancy system has higher reflection ability in the low energy region. For the interstitial defect systems, [Formula: see text] is easy to form on the surface layer, and [Formula: see text] is easy to produce in the inner layer. The [Formula: see text] system has a new additional energy level at the Fermi level, and as the [Formula: see text] is closer to the inner layer, the energy range of the additional energy level is also narrower. In the [Formula: see text] system, the new additional energy levels appear at the Fermi level and the intermediate band. The results have positive significance for the design of this advanced structural and functional integrated ceramics. The absorption coefficient and reflection coefficient of [Formula: see text] system are much higher than those of other systems when the energy is greater than 2.5 eV.

Cyano group modulated porous carbon nitride assisted by silver nanowire for boosting photoreduction of aqueous Cr(VI)

Rapid recombination of photogenerated electron-hole pairs and low utilization of visible light are still restricting the photoreduction efficiency of aqueous Cr(VI) of graphitic carbon nitride. In this work, cyano group (-C≡N) modulated porous carbon nitride assisted by silver nanowire was successfully constructed. Caused by the intense electron acceptors of -C≡N, the co-existence of both n-type and p-type semiconductor characteristics was exhibited in -C≡N modulated porous carbon nitride. The built-in electric field derived from the -C≡N modulated p-n homojunction was suitable to promote separation of electron-hole pairs and retain photogenerated charges with stronger redox capability. In addition, the assisted silver nanowire further enhanced the visible light harvesting derived from the surface plasmon resonance effect of silver nanowire. As expected, the distinctive design could synergize p-n homojunction and plasmonic metal/semiconductor, which was beneficial to strengthen photocatalytic reduction of aqueous Cr(VI) under visible light. The photocatalyst with the unique structure displayed an enhanced photocatalytic reduction efficiency of aqueous Cr(VI) under visible light in comparison with the pristine graphitic carbon nitride. After 2.5 h visible light irradiation, the aqueous Cr(VI) was almost removed. The visible light photocatalytic reaction rate constant of Cr(VI) over Ag-CN/KOH-2 is about 13.8 times than bulk g-C3N4.

Effects on the seebeck co-efficient and electrical properties of Tl10-x ATe6 (A= Pb & Sn) in chalcogenide system

The different elements are doping in the tellurium telluride to determine the different properties like electrical and thermal properties of nanoparticles. The chalcogenide nanoparticles can be characteristics by the doping of the different metals which are like the holes. We present the effects of Pb and Sn doping on the electrical and thermoelectric properties of Tellurium Telluride Tl10-xPbxTe6 and Tl10-xSnxTe6(x=1.00, 1.25, 1.50, 1.75, 2.00) respectively, which were prepared by solid state reactions in an evacuated sealed silica tubes. Structurally, all these compounds were found to be phase pure as confirmed by the x-rays diffractometery (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis. The thermo-power or Seebeck co-efficient (S) was measured for all these compounds which show that S increases with increasing temperature from 295 to 550 K. The Seebeck coefficient is positive for the whole temperature range, showing p-type semiconductor characteristics. Similarly, the electrical conductivity (σ) and the power factors have also complex behavior with Pb and Sn concentrations. The power factor (PF=S 2 σ) observed for Tl10-xPbxTe6 and Tl10-xSnxTe6 compounds are increases with increase in the whole temperature range (290 K-550 K) studied here. Telluride’s are narrow band-gap semiconductors, with all elements in common oxidation states, according to (Tl + ) 9 (Pb 3+ )(Te 2- )6 and (Tl + )9(Sn 3+ )(Te 2- )6. Phases range were investigated and determined with different concentration of Pb and Sn with consequents effects on electrical and thermal properties.

Effect of annealing on microstructure evolution and corrosion resistance of an amorphous Cr-Al-C coating

The microstructure evolution of an amorphous Cr-Al-C coating prepared by magnetron sputtering was investigated. With increasing annealing temperature, three kinds of coatings, including amorphous coating, partially crystallized coating ((Cr,Al)2Cx solid solution), and fully crystallized coating (Cr2AlC MAX phase), were obtained. The electrochemical measurements in 3.5 wt. % NaCl solutions indicated that all of the coatings exhibited passivation behaviors, and amorphous coating possessed the lowest passive current density. All the passive films exhibited p-type semiconductor characteristics, and the passive film on amorphous coating provided the best protection due to the presence of a relatively high content of Cr2O3.

Growth characteristics of tin sulphides crystals by the vapour transport method using SnS and sulphur powders: effect of temperature and pressure

Tin sulphide compounds have two different types of 2D layered crystal structures with different electrical conduction types. Tin disulphide with n-type semiconductor characteristics has a 2D crystal structure with hexagonal symmetry, while tin monosulphide (SnS) with p-type semiconductor characteristics has a 2D crystal structure with orthorhombic symmetry. These layered materials have many potential applications such as electronic and optoelectronic devices. Meanwhile, it is known that the growth products of tin sulphides are very sensitive to the process parameters. In this study, the authors investigated the growth phenomena of tin sulphides by the vapour transport method using SnS and sulphur powders because vapour transport reactions are relatively simple and facilitate the understanding of the effects of growth parameters. The growth behaviour of tin sulphides as a function of process temperature and pressure was observed, and the results can be explained in terms of the sulphurisation and reduction of SnS powder during the growth process.

Study on thermoelectric properties of CrI3 monolayer

In this work, the thermoelectric (TE) properties of the CrI3 monolayer are studied using the Boltzmann transport equation based on the energy band from the first-principles calculation. A strong spin-dependent Seebeck phenomenon is found. The positive Seebeck (spin-Seebeck) coefficient at 800 K reaches up to 291 (263) μV K−1 describing the p-type semiconductor character and the figure of merit is as high as 0.95, mainly originating from the unique band structure of the CrI3 monolayer. This indicates that the CrI3 monolayer may be a potential candidate for low dimensional spin TE application.

Isothermal oxidation of Inconel 625 superalloy at 800 and 1000 °C: Microstructure and oxide layer characterization

Superalloys are widely used in applications at high temperatures and severe environments. Inconel 625 is one of the most applied superalloys due to its high oxidation resistance and mechanical properties, however studies in air lab and temperatures not so extreme as 800 °C are still incipient, mainly regarding microstructure characterization and phases formed during aging at high temperatures. The aim of this study was investigating the Inconel 625 isothermal oxidation behavior at 800 and 1000 °C for 120 and 240 h in air lab. Thermodynamic simulation was used to guide microstructural characterization performed by SEM/EDS and XRD techniques. As-received microstructure presented titanium-niobium (carbo)nitrides and precipitates at grain boundaries. After oxidation, the oxide layer was identified as predominantly chromia in all conditions, providing high oxidation resistance, with some manganese oxidation, suggesting spinel MnCr2O4 formation at 1000 °C, besides ABO4 oxide. Internal alumina oxidation was also observed. Delta phase (Nb,Mo)Ni3 was noticed at grain boundaries (800 °C) and at metal/oxide interface for both temperatures as result of chromium depletion. Some spallation zones were observed at 1000 °C, but this fact did not decrease the good oxidation resistance, as observed at 800 °C. Finally, photoelectrochemistry (PEC) result demonstrated a p-type semiconductor character for chromia scale after 120 h at 800 °C, that was associated to the porous oxide layer and delta phase formation.

First-principles study on Al doped 4H-SiC

In this paper, by using first principles calculation based on density functional theory, 4H-SiC heavily doped model was established using CASTEP software. The crystal structure and electronic structure of p-type Al heavily-doped 4H-SiC prepared by laser irradiation of coated Al film have been calculated and studied. The band structure and densities of state corresponding to various doping concentration of Al were analyzed. The results show that the bandgap width decreases with the increase of Al atom doping concentration and the Fermi level enters the valence band, which reflects the characteristics of p-type semiconductor the laser doped 4H-SiC. Combined with the analysis of secondary ion mass spectrometry, the variation of Al doping concentration with depth was obtained. It was found that the uniform doping concentration of Al which is approximately 1×1020 cm–3 is in the depth range of 30 nm. It is proved that the KrF excimer laser can achieve heavy doping of Al atoms in 4H-SiC. With the increase of depth, the laser energy density decreases gradually, and the doping concentration of Al atoms in 4H-SiC decreases. The p-type semiconductor characteristics of 4H-SiC samples prepared by laser irradiation Al film doping were verified, and the variation of Al doping concentration with laser irradiation depth was obtained.

Effect of sulfurization on physical and electrical properties of MoS2 films synthesized by electrodeposition route

Thin films of uniform molybdenum disulphide (MoS2) were produced on conducting glass (FTO) using the electrochemical route from aqueous solution (NH4)2MoS4 then subjected to annealing treatment under argon gas with and without sulfur. The influence of sulfurazation on the structural, morphological, optical, and electrical properties of samples was investigated. Scanning electron microscopy exhibits homogeneous surface of the samples. Furthermore, the sample exposed to sulfur treatment has narrower grains comparing with that annealed without sulfur. Energy dispersive x-ray spectroscopy (EDX) confirmed the existence of the MoS2 films with a 2.1 S/Mo atomic ratio for the samples heated with sulfur and a 1.76 atomic ratio for those annealed without sulfur. Our results showed that the type of conduction (n or p) have been found to be sensitive to the S/Mo ratio. In fact, an excess of sulfur anions induces a p-type conductivity while a lack of sulfur results an n-type conductivity. X-ray diffraction showed that with sulfuration, the (002) plan main peak is shifted to smaller angle. This is in direct relation to the stress due to the excess of sulfur. As a fact, sample with grater grain size (D) shows the lowest microstrain (ε) and dislocation density (δ). Moreover, the band gap energy values confirmed the results found in fact, referring to the UV–vis diffuse reflectivity spectra, the band gap energy value of the thin films with lack of sulfur was 1.76 eV and 1.66 eV for those annealed with sulfur. In addition, according to the Mott–Schottky plots we confirmed that the films treated without sulfur show n-type conductivity with a carrier density of 3.24 × 1022 cm−3 and a flat-band potential of −0.66V. However, the films annealed with sulfur showed a p-type semiconductor character with a 1.46 × 1022 cm−3 carrier density and a −0.24 V flat-band potential.

Electrical properties of Zn(1−x)CoxO dilute magnetic semiconductor nanoparticles

Zn(1−x)CoxO nanoparticles with (x = 0.05, 0.10, 0.15 and 0.20) were prepared by combustion method. Here we report our findings on electrical properties carried out on these materials from room temperature to 500 °C. Thermopower investigations carried out on the materials resulted in Seebeck coefficient showing a transition from positive to negative values with ‘x’ dependent enhancements. The material that exhibits a p-type semiconductor character at room temperature translates into an n-type of semiconductor at higher temperatures beyond 90 °C marked by a first order transition. Electrical resistivity and the activation energy being interrelated are seen to decrease with rising temperature due to increase in charge carrier concentration. Dielectric constant (e) and dielectric loss (tan δ) investigated as a function of frequency showed nearly exponential decline in their values with increasing frequency for all the samples. However temperature dependent ‘e’ and ‘tan δ’ show a peaking behaviour at lower temperatures with increasing trend at higher temperature as a result of increase in dielectric polarization. The DMS materials being ferromagnetic at room temperature are good temperature dependent semiconductors with high dielectric constant.

An Ion-Sensitive Field Effect Transistor Using Metal-Coordinated Zeolite-Templated Carbons as a Three-Dimensional Graphene Nanoribbon Network

Zeolite template carbon (ZTC) is a carbon material composed of a three-dimensional network of graphene nanoribbons (GNR), and thus, is expected to exhibit electronic characteristics identical to those of GNR. ZTC is capable of doping heteroatoms in its structure, which offers the advantage of controlling its electronic properties by the presence of the heteroatoms. In this study, we prepared heteroatom-doped ZTCs and applied them to an ion-sensitive field effect transistor (ISFET), for investigating the effect of heteroatom doping on its electronic properties. The ISFET characteristics of un-doped ZTC include bipolarity, whereas oxygen-doped ZTC shows p-type semiconductor characteristics, and nitrogen-doped ZTC shows n-type characteristics. Furthermore, copper and nitrogen co-doped ZTC exhibits high sensor sensitivity (the change of electric conductivity reaches up to 50%) as a carbon-based ISFET. As a result of the analytical evaluation, a copper-nitrogen complex is formed in the co-doped ZTC, and the electronic interaction between copper and nitrogen atoms is able to change electrochemically. Owing to the presence of the copper-nitrogen complex, the co-doped ZTC shows specific ISFET characteristics.

Theoretical insight into magnetic and thermoelectric properties of Au doped ZnO compounds using density functional theory

Position of impurities at point defects of a compound have an important role in determine the physical or chemical properties of semiconductor materials. Hence, an accurate and efficient theoretical tool is needed in order to have a deep understanding and logic explanation for the physical phenomenon observed. Therefore, first principles calculation was used to investigate the effect of impurities position at point defects of Au atom in the ZnO semiconductor material on thermoelectric and magnetic performance. In this work, density functional theory based on the generalized-gradient-approximation (GGA) and the Boltzmann transport theory have been used to calculate the structural, electronic, magnetic and thermoelectric properties of Au doped ZnO at different point defect's position (interstitial and substitutional). The obtained results give a hexagonal wurtzite structure with the space group of P63mc and the formation energy at the interstitial model indicated 0.2331 eV lower rather than the substitution model. This indicated more stable structure at the interstitial sites with n-type degenerated semiconductor characteristic and behaves as a diamagnetic material with highest electronic thermal conductivity. Whereas, the substitution of Zn by Au produces p-type semiconductor characteristics with the presence of magnetism properties (0.916 μb of total magnetic moment) and enhance the electrical conductivity properties. The Seebeck coefficient obtained is in excellent accord with the experimental data of Au doped ZnO. The result shows that Au doped ZnO can be used in the thermoelectric power generated in magnetic tunnel junction (MTJ) applications.

P- and n-type thermoelectric cement composites with CVD grown p- and n-doped carbon nanotubes: Demonstration of a structural thermoelectric generator

The thermoelectric (TE) behavior and microstructure of p- and n-doped multi-walled carbon nanotube (CNT) filled cement nanocomposites over 3, 7, 14 and 28 days age are reported for the first time. Pristine CNTs with inherent p-type semiconductor characteristics (p-CNT) and n-type Nitrogen-doped CNTs (n-CNT) were incorporated by shear mixing in a cement matrix at 1% by weight of cement and 0.5 water to cement ratio (w/c). CNTs were dispersed initially by ultrasonication using a surfactant and mixed further with the cement powder. Raman, high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), electric and thermoelectric measurements were employed to characterize the p-CNT and n-CNT, as well as the corresponding cement/CNT nanocomposites. The Seebeck coefficient (S) and electrical conductivity (σ) of nanocomposites for 3, 7, 14 and 28 days of sample's age were examined. All the measurements were performed on as received samples after mould casting at each specific age (samples denoted as before drying) and after drying at 80 °C overnight in order to elucidate the significant effect of moisture. The cement/p-CNT nanocomposite exhibited n-type TE behavior before drying due to the water content and the anions stemming from the cementitious matrix. A p-type behavior was observed after drying and elimination of water, due to the inherent p-type characteristics of CNTs. This is realised by plausible electron withdrawing and p-doping mechanism that adsorbed and/ or chemisorbed oxygen species facilitate to the CNT backbone. The 14 days cement/n-CNT exhibited the highest performance in terms of σ and power factor (PF) reaching 1.44 µWm−1K−2 before drying, and 7.64 × 10−3 µW m−1K−2 after drying. The cement/CNT nanocomposites with p- and n-type TE characteristics allowed the construction of a thermoelectric generator (TEG) for plausible large-scale thermal energy harvesting via cement-based structural thermoelectric generators (TEGs).

Cu3 MS4 (M=V, Nb, Ta) and its Solid Solutions with Sulvanite Structure for Photocatalytic and Photoelectrochemical H2 Evolution under Visible-Light Irradiation.

Solid solutions with of Cu3 VS4 with either Cu3 NbS4 or Cu3 TaS4 (Cu3 Nb1-x Vx S4 or Cu3 Ta1-x Vx S4 ) were prepared by a solid-state reaction and adopted a sulvanite structure. Their band gaps were 1.6-1.7 eV corresponding to the absorption of a wide range of visible light. Ru cocatalyst-loaded Cu3 MS4 (M=V, Nb, Ta), Cu3 Nb1-x Vx S4 , and Cu3 Ta1-x Vx S4 showed photocatalytic activities for sacrificial H2 evolution under visible-light irradiation. Most solid solutions showed better activities than the single-component Cu3 MS4 (M=V, Nb, Ta). Cu3 MS4 (M=V, Nb), Cu3 Nb1-x Vx S4 , and Cu3 Ta1-x Vx S4 also functioned as photoelectrodes and gave cathodic photocurrents under visible-light irradiation, indicating a p-type semiconductor character. Cu3 Nb0.9 V0.1 S4 showed the best photocatalytic and photoelectrochemical performances. When Ru-loaded Cu3 Nb0.9 V0.1 S4 was used as a photocathode with a CoOx -loaded BiVO4 photoanode, photoelectrochemical water splitting proceeded under simulated sunlight irradiation without an external bias.

Electrical Doping Effect of Vacancies on Monolayer MoS2

Doping of transition-metal dichalcogenides (TMDCs) is an effective way to tune the Fermi level to facilitate the band engineering required for different types of devices. For TMDCs, a controversy abounds with regard to the doping role played by vacancy-type defects. Here, we report a detailed study based on first-principles calculations proposing that the native sulfur vacancies (VS) can significantly alter the electrical doping level in MoS2 and tune the material to exhibit conventional n- or p-type semiconductor characteristics. In particular, we reveal that the lower concentration of the single VS (2.8 and 6.3%) yields p-type characteristics, whereas the higher concentration of the single VS or a cluster of VS (12.5, 18.8, and 25.0%) yields n-type characteristics. The trend is consistent with previous X-ray photoelectron spectroscopy and scanning tunneling microscopy results. Employing this method of tuning the electron doping level, we modeled a commonly used metal–semiconductor interface to demonstra...

Passive film on 2205 duplex stainless steel studied by photo-electrochemistry and ARXPS methods

The passive film formed on 2205 duplex stainless steel in pH 8.59 borate buffer solutions was studied by photo-electrochemical techniques and Mott-Schottky analysis. The passive film displays both n-type and p-type semiconductor character in different potential regions of the passive state. The band gap energy of barrier layer of the passive film was 2.4∼2.75 eV. Additionally, the composition of passive film was analyzed by AR-XPS; at -400∼100 mVSCE and above 600 mVSCE Fe2O3, Fe3O4, FeOOH and CrO3 dominate the passive film, showing n-type semi-conductivity; while at 100∼600 mVSCE the passive film comprises FeO, Cr2O3 and Cr(OH)3, exhibiting p-type semi-conductivity.

Effect of sulfur quantity in post-treatment on physicals and electrical properties of electrodeposited Kesterite Cu2ZnSnS4 thin films

In this work, thin films of Cu2ZnSnS4 (CZTS) have been successfully electrodeposited onto FTO substrate. The films are post-sulfurized with different amount of sulfur varied from 0 to 0.5 g at 550 °C under N2 atmosphere. Effect of sulfur quantity during the annealing treatment on structural, morphological, optical and electrical properties of CZTS films have been investigated using various techniques. XRD analysis shows that CZTS thin film annealed at 550 °C in the presence of 0.3 g of sulfur element exhibited the best crystalline quality of kesterite phase with (112) preferential orientation. This result was confirmed by Raman spectroscopy. Surface morphology studied by scanning electron microscopy revealed that the post-sulfurization and especially the quantity of sulfur have a significant effect on the surface and roughness of thin films. According to the UV–Vis measurements, all films show high absorption in the visible region (~ 104 cm− 1) with a direct energy band gap ranging from 2.18 to 1.65 eV, which depends on the sulfur amount during the post-sulfurization. Finally, the electrical characterization by means of electrochemical impedance spectroscopy was carried out to analyze the capacitive nature of CZTS/Na2SO4 interface. This interface was modeled by an equivalent circuit approach. From the Mott–Schottky plot, the flat band potential and the acceptor density for CZTS thin films are determined. All the films demonstrated a p-type semiconductor character with a carrier density varying between 1016 and 1020 cm− 3.