P-type SnO Research Articles

Preparation and characterization of p-type transparent conducting SnO thin films

P-type transparent conducting SnO thin films with enhanced electronic properties were directly prepared using rf magnetron sputtering without post-deposition annealing. The preparation conditions were systemically investigated. The electronic properties, optical properties, structure and surface morphologies of the films were characterized. It was observed that the structure of the films has a great effect on the films׳ conductivity. A transparent p-n junction diode was obtained by growing an n-type SnO2:Sb film on a p-type SnO film deposited on a SiO2(100) substrate. The diode exhibits a distinct I–V rectifying characteristic, indicating that the SnO thin film and the corresponding fabrication method hold promise for use in industrial applications.

Effects of the active layers deposition temperature on the electrical performance of p-type SnO thin-film Transistors

We investigated the effects of the active layers deposition temperature on the electrical performance of p-type tin-oxide thin-film transistors (TFTs). Negligible currents flowed between the source and the drain electrodes in the devices with tin-oxide thin films deposited at 60 °C and 220 °C, but devices with tin-oxide thin films deposited at 100, 140, and 180 °C exhibited typical p-type characteristics. For deposition temperatures ranging from 100 to 180 °C, the field-effect mobility decreased and the turn-on voltage moved in the negative direction as the deposition temperature was increased, which was mainly attributed to a decrease in the grain size based on the grainboundary charge-trapping mechanism. Our experimental results show that it is very important to optimize the active layers deposition temperature to improve the electrical performance in p-type tin-oxide TFTs.

Sputtering deposition of P-type SnO films with SnO₂ target in hydrogen-containing atmosphere.

In this work, we had investigated sputtering deposition of p-type SnO using the widely used and robust SnO2 target in a hydrogen-containing reducing atmosphere. The effects of the hydrogen-containing sputtering gas on structures, compositions, optical, and electrical properties of deposited SnOx films were studied. Results show that polycrystalline and SnO-dominant films could be readily obtained by carefully controlling the hydrogen gas ratio in the sputtering gas and the extent of reduction reaction. P-type conductivity was unambiguously observed for SnO-dominant films with traceable Sn components, exhibiting a p-type Hall mobility of up to ∼3 cm(2) V(-1) s(-1). P-type SnO thin-film transistors using such SnO-dominant films were also demonstrated.

Fabrication of p-n junction diode using SnO/SnO2 thin films and its device characteristics

Present study demonstrates the feasibility of using oxides of Sn to fabricate the p-n junction diode and reports the device characteristics. Reactive thermal evaporation method was used to fabricate the p-type SnO and n-type SnO2 multilayer thin films. The x-ray diffraction (XRD) and Raman spectra depict the presence of both SnO and SnO2 layers. The interface of the p-n junction analyzed by cross-sectional transmission electron microscope (TEM) images and selected area electron diffraction (SAED) pattern confirmed the presence of SnO-SnO2 layers. The diode shows rectifying current-voltage characteristics with forward threshold voltage of 3.5 V.

Homo-Junction pn Diode Using p-Type SnO and n-Type SnO2 Thin Films

Tin oxide thin films are of great interest for device applications, but in spite of their good optical transparency and outstanding semiconductor properties, stable p-type tin oxide needs to be developed. In this study both p-type SnO and n-type SnO2 thin films were deposited by reactive rf magnetron sputtering using Sn target in Ar and O2 gas mixture. The structural, electrical, and optical properties of both p-type SnO and n-type SnO2 thin films were analysed. The transparent homo-junction pn diode was also fabricated and it showed a fairly good rectification behavior with a turn-on voltage of 2.3 V.

Electroforming-free resistive switching memory effect in transparent p-type tin monoxide

We report reproducible low bias bipolar resistive switching behavior in p-type SnO thin film devices without extra electroforming steps. The experimental results show a stable resistance ratio of more than 100 times, switching cycling performance up to 180 cycles, and data retention of more than 103 s. The conduction mechanism varied depending on the applied voltage range and resistance state of the device. The memristive switching is shown to originate from a redox phenomenon at the Al/SnO interface, and subsequent formation/rupture of conducting filaments in the bulk of the SnO layer, likely involving oxygen vacancies and Sn interstitials.

Ferromagnetic spin-order in p-type N-doped SnO2 films prepared by thermal oxidation of SnNx

N-doped SnO2 films were synthesized by oxidative annealing of sputtered SnNx films with various temperatures. The content of the residual N in SnO2:N films decreases with the increase of temperature. N atom is incorporated well at the O lattice site and red-shifts the band-gap by the formation of impurity bands. All the films show p-type conduction and the highest hole concentration is 2.08×1019cm−3 in the sample obtained at 400°C, indicating an effective way to alleviate the self-compensation effect by thermal oxidation. The substituted incorporation of N can also enhance the ferromagnetism and the largest saturation magnetization is 10.1emu/cm3. Theoretical calculations based on the density-functional theory suggest that the ferromagnetism is most likely due to the double exchange mechanism through the p–p interaction. Meanwhile, the ferromagnetic coupling competes with antiferromagnetic coupling as the N–N distance changes, causing the nonmonotonic variation of saturation magnetization.

Study on Preparation and Application Performance of P-Type Conducting SnO<sub>2</sub> Ceramic Target

To obtain high quality SnO2 film, high conductivity and high quality SnO2 target should be obtained first. In this paper, high-conductivity Sb: SnO2 (ATO) ceramic targets were fabricated using SnO2, Sb2O3 powder as raw material. The chemical composition and morphology of SnO2 targets were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The effect of different forming pressure on the morphology and electrical properties of targets were studied in our paper. The results show that molding pressure has a significant impact on the density of ATO targets and performance during sintering process. When molding pressure is 15 Mpa, the target has the minimum resistivity for 2.38 Ωcm. XRD results show that ATO target possess tetragonal rutile structure with the preferred orientation of (101). XPS indicate that the chemical state of Sn element in the target is Sn4+ and that of Sb is Sb3+. In addition, the shrinkage rate of conductive SnO2 target is 10.34% so that target can be used to sputtering in the magnetron sputter. The preparation process is simple and cost of SnO2 target is low. The transparent conductive SnO2 thin film was successfully deposited on glass substrate with good performance of high hole concentration and low resistivity of 3.334×1019 cm-3 and 3.588 Ω·cm, respectively. The average transmission of p-type SnO2 films was above 80% in the visible light range.

Tin oxide with a p–n heterojunction ensures both UV and visible light photocatalytic activity

Tuning of the tin oxide (SnO/SnO2) heterojunction (TOHJ) has been made possible by heating the as-prepared p-type SnO semiconductor in air in a controlled fashion. Thus a better photocatalytic activity for dye degradation under UV, visible as well as solar light irradiation was achieved. Multiple reflection of light and the TOHJ of SnO plates facilitate the photocatalysis reactions.

Transparent p-type SnO nanowires with unprecedented hole mobility among oxide semiconductors

p-type tin monoxide (SnO) nanowire field-effect transistors with stable enhancement mode behavior and record performance are demonstrated at 160 °C. The nanowire transistors exhibit the highest field-effect hole mobility (10.83 cm2 V−1 s−1) of any p-type oxide semiconductor processed at similar temperature. Compared to thin film transistors, the SnO nanowire transistors exhibit five times higher mobility and one order of magnitude lower subthreshold swing. The SnO nanowire transistors show three times lower threshold voltages (−1 V) than the best reported SnO thin film transistors and fifteen times smaller than p-type Cu2O nanowire transistors. Gate dielectric and process temperature are critical to achieving such performance.

Type Inversion and Certain Physical Properties of Spray Pyrolysed SnO2:Al Films for Novel Transparent Electronics Applications

Aluminium doped tin oxide films have been deposited onto glass substrates by using a simplified and low cost spray pyrolysis technique. The Al doping level varies between 0 and 30 at.% in the step of 5 at.%. The resistivity (ρ) is the minimum (0.38 Ω cm) for 20 at.% of Al doping. The possible mechanism behind the phenomenal zig-zag variation in resistivity with respect to Al doping is discussed in detail. The nature of conductivity changes from n-type to p-type when the Al doping level is 10 at.%. The results show that 20 at.% is the optimum doping level for good quality p-type SnO2:Al films suitable for transparent electronic devices.

Fabrication of p-type SnO2 films via pulsed laser deposition method by using Sb as dopant

p-Type transparent conducting antimony-doped tin oxide (ATO) thin films were successfully fabricated on quartz glass substrates by pulsed laser deposition using a 20at.% Sb doped SnO2 ceramic target. The growth temperature was varied from 500 to 800°C, after deposition, the thin films were rapidly annealed at 500°C in air for 2h. Several analytical tools such as X-ray diffraction (XRD), Hall measurements, four-point probe, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectrophotometer were used to explore the causes of the changes in optoelectronic properties and surface micrographs. The Sb-doped SnO2 film prepared at 700°C possessed the lowest resistivity of 0.87Ωcm with a Hall mobility of 0.65cm2v−1s−1 and hole concentration of 1.01×1019cm−3, while the average transmittance is about 85% in the visible light region (400–800nm). Furthermore, SnO2-based p-n homojunction was fabricated by deposition of a Sb-doped p-type SnO2 layer on a Sb-doped n-type SnO2 layer.

Effect of radio frequency power on the properties of p-type SnO deposited via sputtering

P-type SnO thin films were fabricated via radio frequency (rf) reactive magnetron sputtering on borosilicate substrates, with an Sn target and Ar/O2 gas mixture. As the rf power increased, the structural defects were formed in SnO thin films lowering the optical absorption edge. It was found that the SnO thin films showed a short-range ordered crystalline structure and the crystallinity was slightly improved as the rf power increased. The electrical conductivity of SnO thin films was increased as the rf power increased and at 300W, the conductivity was 0.048(Ωcm)−1, but it exhibited the very poor mobility of 0.02cm2/Vs.

Sputtering deposition of P-type SnO films using robust Sn/SnO2 mixed target

Although SnO is a promising p-type oxide material for thin-film transistors (TFTs), the development of the TFT-industry-compatible deposition technique and materials for p-type SnO films is still an issue. In this work, we demonstrate the preparation of pure and p-type SnO films using the Sn/SnO2 mixed target and the conventional magnetron sputtering technique. By controlling the sputtering conditions, the deposited films can be tuned from pure n-type SnO2 to pure p-type SnO. Compared to other sputtering target materials (e.g., pure SnO and Sn), the Sn/SnO2 mixed targets can be fabricated by the high-temperature high-pressure pressing/sintering technique and have higher density and robustness more suitable for real uses. The p-type mobility of SnO films obtained here is comparable to results of other approaches, showing the feasibility of this method.

Investigation of p-type SnO2:Zn films deposited using a simplified spray pyrolysis technique

Zinc doped SnO2 films were prepared using a simplified spray technique and the influence of dopant concentration on structural, electrical, optical and surface morphological properties were analysed in detail. XRD results showed that all the films were polycrystalline SnO2 with tetragonal rutile structure. The transition of preferential orientation from (211) to (101) plane was found to take place beyond 20at.% of Zn doping level. Hall measurements showed that the films exhibited p-type conductivity when the doping concentration was increased beyond 20at.%. The average transmittance of the SnO2:Zn films were in the range of 80–90% in the visible region. The enhancement in the PL emission can be correlated with the decrease in the grain size observed from the SEM images and the sharpening of defect related peaks supplemented the formation of trapped states (introduction of dangling bonds) at higher Zn concentrations.

Record Mobility in Transparent p-Type Tin Monoxide Films and Devices by Phase Engineering

Here, we report the fabrication of nanoscale (15 nm) fully transparent p-type SnO thin film transistors (TFT) at temperatures as low as 180 °C with record device performance. Specifically, by carefully controlling the process conditions, we have developed SnO thin films with a Hall mobility of 18.71 cm(2) V(-1) s(-1) and fabricated TFT devices with a linear field-effect mobility of 6.75 cm(2) V(-1) s(-1) and 5.87 cm(2) V(-1) s(-1) on transparent rigid and translucent flexible substrates, respectively. These values of mobility are the highest reported to date for any p-type oxide processed at this low temperature. We further demonstrate that this high mobility is realized by careful phase engineering. Specifically, we show that phase-pure SnO is not necessarily the highest mobility phase; instead, well-controlled amounts of residual metallic tin are shown to substantially increase the hole mobility. A detailed phase stability map for physical vapor deposition of nanoscale SnO is constructed for the first time for this p-type oxide.

Fabrication of p-Type SnO Thin-Film Transistors by Sputtering with Practical Metal Electrodes

P-type thin-film transistors using polycrystalline tin monoxide (SnO) active layers were achieved by an industry-compatible sputtering technique with a SnO ceramic target. The SnO films clearly exhibited p-type conduction with the p-type Hall mobilities of 1–4 cm2 V-1 s-1 and hole concentrations of 1017–1018 cm-3. The physical and chemical structures of SnO films were characterized by X-ray diffraction analysis and X-ray photoemission spectroscopy. It is concluded that amorphous and SnO-dominant films were obtained as deposited. Further annealing at ≤300 °C induces crystallization but no major chemical reaction. The transmission line method was adopted to characterize the contact resistance between SnO layers and various metal electrodes. Results show that Mo and Ni could be used as effective electrodes for p-type SnO, avoiding the use of noble metals. Finally, p-type SnO TFTs using practical metal electrodes were fabricated, where a field-effect mobility of up to 1.8 cm2 V-1 s-1 and an on/off current ratio of >103 were achieved.

Volatile Gas Sensing Properties of Phase and Composition Gradient SnOx Thin Films by Combinatorial Sputter Deposition

Compositionally gradient tin oxide thin films were prepared by co-sputtering from tin and tin oxides targets. After annealing at 450°C, gradient crystalline phases of SnO and SnO2 were fabricated on a single sensor. Acetone, ethanol, and ethylene were utilized to investigate sensing properties of the gradient tin oxide sensor. Coexisting p-type SnO and n-type SnO2 affect the direction of electrical resistance and the response during gas reaction and recovery. Construction of gradient tin oxide film in terms of composition and crystalline phase demonstrates the design of a gas sensor for the selective gas detection via the combinatorial approach.

P-type conduction in nitrogen-doped SnO2 films grown by thermal processing of tin nitride films

p-type nitrogen-doped SnO2 (SnO2:N) films were grown by thermal processing of amorphous tin nitride films at temperatures between 350 and 500 ∘C in flowing O2–Ar gas mixture. From high-resolution X-ray photoelectron spectroscopy (XPS) and X-ray diffraction patterns, it is deduced that the N atoms replace the O atoms in the SnO2 lattice. The N dopant is more tightly bound in SnO2:N at higher thermal oxidation temperatures deduced from the XPS results. The hole concentration obtained at an oxidation temperature of 400 ∘C is 1.87×1019 cm−3, which is dramatically enhanced compared to previous reports. Our results indicate that the high-temperature thermal oxidation of tin nitride is a facile and effective route to alleviate the self-compensation effect, reduce the content of γ-N2 double donors, and reinforce the stability of N dopant in the SnO2:N films.

Transparent p-type AlN:SnO2 and p-AlN:SnO2/n-SnO2:In2O3 p-n junction fabrication

This study produced transparent p-type AlN-doped SnO2 thin films by annealing sputtered sandwich SnO2/AlN/SnO2 thin films. Both Al3+-Sn4+ and N3−O2− substitution reactions—which are the main sources for the hole carriers—were identified by XPS analysis. The hole concentration of the p-type AlN:SnO2 thin films was as high as 1.074 × 1019 cm−3. Using the produced p-AlN:SnO2 thin film, transparent p-AlN:SnO2/n-SnO2:In2O3 p-n junctions were fabricated and characterized as follows: (1) A low leakage current (2.97 × 10−5 A at −5 V); (2) a 2.17 eV turn-on voltage; and (3) a low ideality factor (12.2).