P-type Electrical Conductivity Research Articles

Thin film Sn2S3 via chemical deposition and controlled heating – Its prospects as a solar cell absorber

As a semiconductor of “earth-abundant” elements, Sn2S3 with a bandgap (Eg) close to 1 eV merits attention, but a method to prepare phase-pure thin film remains elusive. We report the formation of Sn2S3 thin film of 360 nm in thickness by heating chemically deposited tin sulfide thin films at 450 °C during 30–45 min in presence of sulfur at a pressure, 75 Torr of nitrogen. Energy dispersive x-ray emission spectra and grazing incidence x-ray diffraction established a reaction route for this conversion of SnS completely to Sn2S3 via an intermediate phase, SnS2. The optical bandgap of the material is 1.25 eV (indirect) and 1.75 eV (direct, forbidden). The optical absorption suggests a light-generated current density of 30 mA/cm2 for the Sn2S3 film (360 nm) as a solar cell absorber. Thin film Sn2S3 formed in 30 min heating has a p-type electrical conductivity in the dark of 1 × 10−4 Ω−1 cm−1, which increases to 3 × 10−4 Ω−1 cm−1 in 0.2 s under 800 W/m2 tungsten-halogen illumination. An estimate made for its mobility-lifetime product is, 6 × 10−6 cm2 V−1. We discuss the prospects of this material for solar cells.

Physical and chemical study of the dependence of substrate temperature on properties of Cu3SbS3 thin films

This work highlights the effect of substrate temperature on the properties of Cu3SbS3 thin films grown on unheated and heated glass substrates, by vacuum thermal evaporation. The as-deposited film is elaborated at room temperature (25 °C). The heated substrates are processed at various temperatures, ranging from 70 °C to 180 °C. Cu3SbS3 powder was successfully synthesized by direct fusion method. The obtained films were assayed for their structural, morphological, optical and electrical properties using several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray Spectrometry analysis (EDXS), UV‐VIS‐NIR spectrophotometer and hot probe method, respectively. First, the XRD analysis shows amelioration in the structural properties by increasing the substrate temperature. The microstructural parameters of all films were investigated such as crystallite size, strain and dislocation density. Second, the optical analysis shows that thin films have high absorption coefficients ranging between 105 and 106 cm−1. In addition, as per the models of Wemple–DiDomenico and Spitzer-Fan other optical and dielectric constants were estimated. Finally, the electrical study reveals that the p-type electrical conductivity is verified in all the samples.

Combinatorial Tuning of Structural and Optoelectronic Properties in CuxZn1−xS

Summary P-type transparent conductors (TCs) are important enabling materials for optoelectronics and photovoltaics, but their performance still lags behind n-type counterparts. Recently, semiconductor CuxZn1−xS has demonstrated potential as a p-type TC, but it remains unclear how properties vary with composition. Here, we investigate CuxZn1−xS across the entire alloy space (0 ≤ x ≤ 1) using combinatorial sputtering and high-throughput characterization. First, we find a metastable wurtzite alloy at an intermediate composition between cubic endpoint compounds, contrasting with solid solutions or cubic composites (ZnS:CuyS) from the literature. Second, structural transformations correlate with shifts in hole conductivity and absorption; specifically, conductivity increases at the wurtzite phase transformation (x ≈ 0.19). Third, conductivity and optical transparency are optimized within a "TC regime" of 0.10

An attempt to co-deposit photovoltaic quality CuInSe2 thin films: effect of surfactant and deposition potential

CuInSe2 (CISe) thin films were prepared by single step electrodeposition technique using citrate-SDS electrolyte. Preliminary studies revealed that the initial deposition conditions have significant influence over the composition, film quality and the addition of SDS in the citrate electrolyte enhances adhesion, smoothness and eliminates multinuclear growth. To explore the capability of the citrate-sodium dodecyl sulfate (SDS) electrolyte, the CISe thin films deposited at various potentials were annealed at 300 °C in nitrogen atmosphere. The structural, morphological and compositional properties of the annealed CISe thin films were compared. Finally, CISe thin film deposited at − 0.65 V/SCE exhibiting the p-type electrical conductivity was confirmed by Mott–Schottky (M–S) and photoelectrochemical (PEC) studies.

Study on mechanically alloyed tin telluride screen-printed films for optoelectronic device applications

Narrow band gap semiconductor tin telluride (SnTe) was synthesized by mechanical alloying and its film was deposited on glass substrates by the economically and commercially feasible screen-printing technique. Deposition of the film was followed by sintering. Different analytical techniques were utilized to study the structure, surface morphology, elemental, optical and electrical characteristics of the film. X-ray diffraction analysis confirms that the film is polycrystalline in nature and exhibits rock salt type structure with preferred orientation of grains along (200) direction. EDAX spectrum confirms the presence of Sn and Te elements in the film. SEM image shows that the film exhibits uniform surface. The energy band gap of the film was determined by reflection spectra. The film is found to have a direct band gap of 0.37 eV. The dark electrical conductivity and activation energy of the film were measured in temperature range 300–380 K. Hall Effect measurement indicates that the film has p-type electrical conductivity.

An efficient wide range photodetector fabricated using a bilayer Bi2S3/SnS heterojunction thin film

This study presents a detailed optoelectronic investigation on the bilayer Bi2S3/SnS heterojunction photodetector. The Bi2S3 and SnS nanostructures were synthesized by an ultrasonication method and deposited in the form of thin films by a thermal evaporation system to fabricate the photodetectors. The performed optoelectrical measurements showed that the Bi2S3 and Bi2S3/SnS photodetectors are respectively n- and p-type electrical conductivity. This finding was further confirmed by current–voltage (I–V) analysis, Mott–Schottky plots and photoresponse measurements. According to the obtained gain and sensitivity values, the Bi2S3/SnS heterojunction provides a higher photon-to-electrical carrier conversion relative to the Bi2S3 photodetectord due to the enhanced photogeneration of electron–hole pairs and separation of the photoinduced charge carriers under the influence of the electric field build-in at the heterojunction’s interface. The heterojunction exhibited a remarkable photoresponse from 400 to 800 nm by giving the photocurrent gain (G), sensitivity (S), and external quantum efficiency (EQE) values of 8460%, 450% and 45%, respectively. The obtained results represent the Bi2S3/SnS heterojunction photodetector as a potential candidate for devising high-performance optoelectronic devices.

Влияние легирования ванадием на термоэлектрические свойства сплавов Гейслера Fe-=SUB=-2-=/SUB=-Ti-=SUB=-1-x-=/SUB=-V-=SUB=-x-=/SUB=-Sn

In this work the results of an experimental study of Fe2Ti1-xVxSn alloys (x = 0; 0.06; 0.15; 0.2) are presented. According to the temperature dependencies of the electrical conductivity, Seebeck coefficient and thermal conductivity, it is established, that the studied compositions exhibit transport properties typical for semiconductors. The substitution of V at the Ti site leads to a change of the p-type electrical conductivity behavior to n-type; the pristine sample of Fe2TiSn has the best thermoelectric properties.

P-type β-MoO2 nanostructures on n-Si by hydrogenation process: synthesis and application towards self-biased UV-visible photodetection

We report on the synthesis and UV–vis photodetection application of p-type MoO2 nanostructures (NSs) on Si substrate. β-MoO2 NSs have been synthesized from previously grown α-MoO3 structures/n-type Si via a hydrogenation process at 450 °C. After hydrogenation, the α-MoO3 structures were completely converted into β-MoO2 NSs without the presence of sub-oxidized phases of molybdenum oxide. The as-grown NSs exhibited very good p-type electrical conductivity of ≈2.02 × 103 S–cm−1 with hole mobility of ≈7.8 ± 1.3 cm2–V−1–Sec−1. To explore optoelectronic properties of p-type β-MoO2 NSs, we have fabricated a p-MoO2/n-Si heterojunction photodetector device with Au as the top and Al as the bottom contacts. The device exhibits peak photoresponsivity of ≈0.155 A W−1 with maximum detectivity ≈1.28 × 1011 cm–Hz1/2–W−1 and 44% external quantum efficiency around ≈436 nm, following the highest photoresponse (Iph/Id ≈ 6.4 × 102) and good response speed (rise time ∼29 ms and decay time ∼38 ms) at −1.5 V. Importantly, this device also shows good self-powered high-speed (rise time ∼47 ms and decay time ∼70 ms) photodetection performance with peak responsivity and detectivity of ≈45 mA W−1 and ≈4.05 × 1010 cm–Hz1/2–W−1, respectively. This broadband UV-visible light detection feature can be attributed to the coordinated effects of MoO2 band-edge absorption, interfacial defects and self absorption in Si. The photodetection behavior of the device has been understood by proposed energy-band diagrams with the help of an experimentally derived work function, band gap and valence band maximum position of MoO2 NSs.

High performance p-type transparent LaCuOS thin film fabricated through a hydrogen-free method

It is a crucial and also well-known challenge to develop p-type transparent semiconducting oxides (TSOs) for future optoelectronics including transparent electronics. In this work, a novel hydrogen-free thin film fabrication method is proposed and succeeded to prepare high quality single phase p-type oxychalcogenide LaCuOS thin film in a safe, economically efficient and easy way. It differs from conventional processes for oxychalcogenide films that involve the usage of toxic and hydrogen-containing H2S gas as well as the tedious and highly costly sputter targets preparation. Instead, we combine a unique co-sputtering of La2O3 and Cu and sulfurization process to make the oxychalcogenide thin films free from any n-type hydrogen doping influence. The achieved p-type electrical conductivity of 0.3Scm−1 is much higher than other polycrystalline LaCuOS films and among the best non-doped p-type TSOs reported so far. Furthermore our films also demonstrate great room temperature photoluminescence. The success of this newly developed thin film fabrication process also lays the groundwork to the fabrication of other highly conductive p-type oxychalcogenides thin films.

Two-stage processed Cu4SnS4 thin films for photovoltaics - Effect of (N2 + S2) pressure during annealing

In this paper, we report the fabrication of Cu4SnS4 thin films by annealing chemically deposited SnS–CuS precursors at 823 K for 90 min, and we studied the effect of the (N2 + S2) pressure during annealing on the growth and properties of the Cu4SnS4 films. Films prepared at a (N2 + S2) pressure of 1.3 kPa exhibited an orthorhombic crystal structure with lattice parameters of a = 1.371 nm, b = 0.766 nm, and c = 0.643 nm, a grain size of 3–6 μm, a direct optical band gap of 1.0 eV, p-type electrical conductivity, and a hole mobility of 69.5 cm2 V−1 s−1. Increasing the (N2 + S2) pressure from 1.3 kPa to 66.7 kPa increased the grain size to more than 6 μm and the hole mobility to 150 cm2 V−1 s−1 at 26.7 kPa and then decreased to 86 cm2 V−1 s−1 at 66.7 kPa. Further increasing the (N2 + S2) pressure to 101.3 kPa resulted in the formation of a monoclinic Cu2SnS3 secondary phase. This study reveals that an annealing temperature of 823 K and a (N2 + S2) pressure of 1.3–66.7 kPa are the optimized conditions to obtain large-grained Cu4SnS4 films free of secondary phases with good optical and electrical properties.

Large-grained Sb2S3 thin films with Sn-doping by chemical bath deposition for planar heterojunction solar cells

Herein, the growth of large-grained and compact Sb2S3 thin films with good electrical properties by Sn doping using a chemical bath deposition (CBD) and annealing approach is detailed. Sn-doped Sb2S3 thin films were prepared using the CBD method with SbCl3, SnCl2.2H2O, and Na2S2O3 as source materials, and ethylenediamine tetraacetic acid (EDTA) as the complexing agent at 40 ° C for 3 h followed by annealing at 250 °C for 30 min under Ar ambience. Un-doped Sb2S3 films exhibited an orthorhombic crystal structure with lattice parameters of a= 1.142 nm, b= 0.381 nm, and c= 1.124 nm, crystalline grain sizes of 100 nm, a direct optical band gap of 1.70 eV, p-type electrical conductivity with high electrical resistivity, and low hole mobility. With Sn doping, a significant increase in the grain size of the films from 6 to >10μm was observed with increasing Sn content from 1.0 to 5.5 at% followed by a decrease in the grain size. The direct optical band gap of the films was 1.71–1.72 eV. By varying Sn at%, the electrical resistivity of the films decreased, and hole mobility increased from 117 to 205 cm2 V−1 s−1 up to 5.5 at% and decreased to 166 cm2 V−1 s−1 at 7.2 at%. With the addition of 1.0–5.5 at% Sn in the Sb2S3 films, the grain growth and electrical properties of the films were drastically enhanced, which is beneficial for the fabrication of planar heterojunction solar cells.

Two-stage processed CuSbS2 thin films for photovoltaics: Effect of Cu/Sb ratio

In recent years, CuSbS2 has attracted significant research interest because of its direct optical band gap of 1.5 eV, high optical absorption coefficient, p-type electrical conductivity, and composition involving earth-abundant and non-toxic precursor elements. We prepared CuSbS2 thin films by annealing chemically grown Sb2S3 and sputter deposited Cu (Sb2S3/Cu) stacks in a graphite box, and studied the effect of the Cu/Sb ratio on the growth and properties of these films by varying the thickness of Cu while keeping the thickness of Sb2S3 constant. The Cu/Sb ratio significantly impacted the phase purity, grain growth, and morphology of the CuSbS2 films. The CuSbS2 films prepared with a Cu/Sb ratio of 0.78 showed some unreacted Sb2S3 and nonuniform grain growth. Upon increasing the Cu/Sb ratio from 0.85 to 0.97, the Sb2S3 phase was consumed completely, and phase-pure CuSbS2 with homogeneous grain formation was obtained. These films exhibited an orthorhombic crystal structure with the (410) preferred orientation. Further increase in the Cu/Sb ratio from 1.28 to 1.52 resulted in a change in the growth direction along the (200) plane and the formation of several micron-sized grains with a compact morphology and Cu3SbS4 secondary phase. The direct optical band gap of the films decreased from 1.52 to 1.48 eV when Cu/Sb ratio was increased from 0.91 to 1.28. The films exhibited p-type electrical conductivity and their electrical resistivity decreased with increasing Cu/Sb ratio. From this investigation it was clear that deviation in the Cu/Sb ratio from the stoichiometric proportion leads to inhomogeneous grain growth of CuSbS2 films, which affect the performance of devices using these films.

Characterization of single step electrodeposited Cu2ZnSnS4 thin films

Electrodeposited copper zinc tin sulfide (CZTS) thin films grown on conducting glass substrates are investigated in this report. The photoelectrochemical cell (PEC), optical, structural and morphological properties of the deposited films have been characterized. PEC measurements of the CZTS thin film showed p-type electrical conductivity. Optical measurement showed that the transmittance of CZTS films is observed to about 0.5–3.4% in the wavelength range 300–1100 nm. It is also observed that the absorbance of the CZTS thin films rapidly increases in the wavelength range 580–620 nm and then it decreases slowly. The band gap of the CZTS thin film is observed to be in the range 1.6–2.2 eV. The transmittance and band gap decreases upon annealing at different temperatures but the absorbance and the grain size increases due to the improvement of crystalline quality upon annealing. From the X-ray diffraction study, the CZTS films are found to be polycrystalline with (112), (200), (105), (204), (312), (220) orientations of the tetragonal structure. The average crystallite size is estimated to 23 nm for as-deposited film, 26 nm for annealed at 300 °C and 40 nm for annealed at 350 °C. It is found from SEM study that the precursor film shows non-uniform distribution of agglomerated particles with well-defined boundaries. As the annealing temperature increases, the crystallization of the films is observed to improve, and hence the morphology of as-deposited precursor film is observed to change into the larger flat grains upon annealing.

Tuning the electrical properties of the p-type transparent conducting oxide Cu1\u2212xCr1+xO2 by controlled annealing

Off-stoichiometric copper chromium oxide delafossite received lately a great interest due to its high p-type electrical conductivity and adequate optical transmittance in the visible range. However, for a suitable integration in active devices such as p-n junctions, transistors or optoelectronic devices, the electronic properties must be efficiently tailored. Here, post-deposition thermal treatment is proven as an adequate approach for finely controlling the electrical properties of this former degenerate semiconducting material. The energetics of the annealing process are investigated using two different approaches, as a function of the annealing temperature and as a function of the annealing time, allowing the accurate determination of the activation energy of the annealing of defects. By using this method, the electrical carrier concentration was varied in the 1021 – 1017 cm−3 range while the recorded changes in the drift mobility covered three orders of magnitude. Moreover, we demonstrate the ability to accurately manipulate the Fermi level of such materials, which is of great importance in controlling the carrier injection and extraction in optoelectronic active layers.

Stretchable and flexible thermoelectric polymer composites

Polymer composites were manufactured from pristine and oxidized multi-walled carbon nanotubes and ethylene-octene copolymer. The composites had thermoelectric properties and exhibit thermoelectric effect, that is, the conversion of temperature differences into electricity. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy of the multi-walled carbon nanotubes in ethylene-octene copolymer matrix showed that the oxidation with HNO3 or KMnO4 enhanced its p-type electrical conductivity and that the thermoelectric power increase was proportional to the formation of new oxygen-containing functional groups on the surface of carbon nanotubes.

Growth and characterization of Cu3SbSe4 thin films through thermally diffusing Sb2Se3 – CuSe by chemical bath deposition (CBD)

In the present work, Cu3SbSe4 thin films have been successfully synthesized by chemical bath deposition (CBD) involving a sequential deposition of antimony selenide (Sb2Se3) and copper selenide (CuSe) films and then annealing in a vacuum atmosphere. The influence of CuSe deposition time on the previously deposited Sb2Se3 films was investigated to obtain the ternary phase. A study of the structural, morphological, optical and electrical properties of these films was carried out using appropriate characterization techniques. X-ray diffraction analysis revealed that the films show a tetragonal crystalline crystalline structure corresponding to the Permingeatite phase (Cu3SbSe4). The crystal size increases with the CuSe deposition time. It is identified by Raman spectroscopy that at low CuSe deposition times a low concentration of Sb2Se3 coexists in the thin film. The optical band gap energy of these films was evaluated in the range of 0.67–1.18 eV, decreasing by increasing CuSe deposition time. By field-emission scanning electron microscopy (FESEM) a morphological study was carried out, observing that by increasing the deposition time of CuSe there is an increase of agglomerates and decrease the porosity in the samples. An elemental analysis was carried out by energy dispersive X-ray spectroscopy to observe the composition and elemental distribution in the ternary compound. The films showed a p-type electrical conductivity with values between 0.417 and 55.55 (Ω cm−1). The mobility and carrier density were performed by Hall Effect and Thermoelectric measurements observing a slight increase in the values by increasing the time of CuSe deposition. All results obtained for thin films of Cu3SbSe4 suggest that it could be used as an absorber material in a solar cell or thermoelectric material.

Electrical and Optical Properties of Cu2Zn(Fe,Mn)SnS4 Films Prepared by Spray Pyrolysis

We have analyzed the electrical and optical properties of Cu2ZnSnS4, Cu2FeSnS4, and Cu2MnSnS4 films with the p-type electrical conductivity, which were prepared by spray pyrolysis at temperature TS = 290°C using 0.1 M aqueous solutions of salts CuCl2 · 2H2O, ZnCl2 · 2H2O, MnCl2 · 2H2O, FeCl3 · 6H2O, SnCl4 · 5H2O, and (NH2)CS. The energy parameters have been determined from analyzing the electrophysical properties of the films using the model of energy barriers at grain boundaries in polycrystalline materials, and the thickness of intercrystallite boundaries has been estimated. The extent of the influence of the hole concentration p0 in the bulk of crystallites and height E b of the energy barriers between grains on the electrical conductivity has been determined. The optical bandgap width for thin Cu2Zn(Fe,Mn)SnS4 films has been calculated based on analyzing the spectral dependences of the absorption coefficient.

Fabrication of Cu2(ZnxMg1-x)SnS4 thin films by pulsed laser deposition technique for solar cell applications

In this study, the pulsed laser deposition technique was applied for the preparation and characterization of Cu2(ZnxMg1-x)SnS4 (CZMTS) thin films for solar cell applications. The effects of various zinc/magnesium compositional ratios on the properties of the CZMTS thin films were investigated. The field emission scanning electron microscopy studies revealed that the CZMTS thin films exhibited dense, uniform and smooth surfaces. The X-ray diffraction studies on the as-deposited and annealed CZMTS thin films showed the prominent peak from the (112) plane for kesterite phase Cu2ZnSnS4. The Raman studies on the CZMTS thin films further confirmed formation of kesterite phase and beneficial MoS2 layer. Further, the Hall measurement studies on CZMTS thin films confirmed p-type electrical conductivity behavior. The conductivity increased from 2.31S/cm to 7.98S/cm with increased Mg concentration. The X-ray energy dispersive spectroscopy studies revealed formation of stoichiometric thin films. The direct optical band gap for the CZMTS thin films were found to be in the range of 1.3–1.5eV, suggesting their potential application as a low cost and earth abundant thin film solar cell absorber material.

Spin-orbit coupling in manganese doped calcium molybdato-tungstates

The manganese doped calcium molybdato-tungstates with the formula of Ca1-xMnx(MoO4)0.50(WO4)0.50 (x = 0.01, 0.03, 0.05, 0.10, 0.125, and 0.15) were successfully obtained by two-step synthesis using in both steps a solid state reaction route. All ceramics show scheelite-type tetragonal structure with space group I41/a. The electrical and magnetic studies within the temperature range of 2–300K showed a weak p-type electrical conductivity and the paramagnetic state of Mn-doped ceramic materials. With increasing Mn content in samples under study, a change in the short-range interactions from ferromagnetic to antiferromagnetic as well as an increase in the orbital contribution to the magnetic moment, resulting in a strong spin-orbit coupling, were observed. The Brillouin procedure was used to estimate the Landé factor.

Substrate and Mg doping effects in GaAs nanowires.

Mg doping of GaAs nanowires has been established as a viable alternative to Be doping in order to achieve p-type electrical conductivity. Although reports on the optical properties are available, few reports exist about the physical properties of intermediate-to-high Mg doping in GaAs nanowires grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates. In this work, we address this topic and present further understanding on the fundamental aspects. As the Mg doping was increased, structural and optical investigations revealed: i) a lower influence of the polytypic nature of the GaAs nanowires on their electronic structure; ii) a considerable reduction of the density of vertical nanowires, which is almost null for growth on Si(111); iii) the occurrence of a higher WZ phase fraction, in particular for growth on Si(111); iv) an increase of the activation energy to release the less bound carrier in the radiative state from nanowires grown on GaAs(111)B; and v) a higher influence of defects on the activation of nonradiative de-excitation channels in the case of nanowires only grown on Si(111). Back-gate field effect transistors were fabricated with individual nanowires and the p-type electrical conductivity was measured with free hole concentration ranging from 2.7 × 1016 cm−3 to 1.4 × 1017 cm−3. The estimated electrical mobility was in the range ≈0.3–39 cm2/Vs and the dominant scattering mechanism is ascribed to the WZ/ZB interfaces. Electrical and optical measurements showed a lower influence of the polytypic structure of the nanowires on their electronic structure. The involvement of Mg in one of the radiative transitions observed for growth on the Si(111) substrate is suggested.