Tin Monoxide Research Articles

Chemical and Electronic Sensitization Effects Promoted By Noble Metal Nanoparticles on Gas Sensors Based on SnO Nanobelts

IntroductionSemiconducting metal oxides (SMOx) are the most studied materials for gas sensing applications due to their outstanding capacity to detect flammable and toxic gases, and their low-cost processing and ease of handling. [1,2]Many strategies have been developed attempting to achieve materials with improved sensor performance, including surface functionalization. The most common SMOx surface functionalization species are noble metal nanoparticles (NPs) given the possibilities to present both chemical and electronic sensitization effects.[3]This work reports on the gas sensing response of pristine and Pt and Pd decorated stannous oxide nanobelts. The responses of devices to different analytes (H2, CO and NO2) were measured in dry air baseline atmosphere as function of the analyte concentration (1–1000 ppm) and temperature (150-350 °C). Method Stannous oxide nanobelts were synthesized by a carbothermal reduction method using a mixture of SnO2 powder (Sigma-Aldrich, 99.9% purity) and carbon black (Union Carbide, > 99% purity) in the molar ratio of 1.5:1 (SnO2:C) as starting material.[4] The nanoparticles (Pt and Pd) used to functionalize the surface of nanobelts were prepared by the polyol method.Samples were characterized by field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study their morphology and crystalline structure.Suspensions of pristine and functionalized materials were deposited onto interdigitated platinum electrode arrays to perform the gas sensor measurements. The devices were placed in a temperature-controlled tubular furnace chamber, where the electric current was monitored under a constant applied voltage. Synthetic dry air was used as baseline and the analytes (NO2, H2 and CO) were introduced into the chamber using mass flow controllers. Gas sensor measurements were performed ranging from 150 °C to 350 °C. Results and Conclusions SEM and TEM results showed that obtained materials were nanobelts in the SnO phase. Moreover, functionalization with noble metal nanoparticles was successful, presenting disperse nanoparticles (< 15 nm) over nanobelts surface.About the gas sensing measurements, pristine devices are both sensitive and selective for nitrogen dioxide (NO2) molecules between 100 and 250 °C. In addition, both Pd- and Pt- functionalized devices present excellent selectivity to H2 at 300 and 350 °C. Moreover, Pt- functionalized device presented good selectivity for high concentrations of CO (>200 ppm) at low temperatures (100 and 150 °C). Then, results showed that noble metal decorated devices exhibited enhanced chemical sensitization, resulting in increased sensitivity upon exposure to reducing gases at different working temperatures. Differences in enhancement levels are attributed to strong electronic sensitization effects that are dependent on the respective Pt and Pd work functions and the unique SnO band structure, characterized by a small band gap (0.6 eV). Values showed that while Pt0 and Pt2+ promotes a high potential barrier with SnO nanobelts, Pd0 does not have this effect. Based on these findings, we propose an array based on pristine and NPs-functionalized SnO structures capable of detecting and distinguishing reducing and oxidizing gases. Furthermore, electronic sensitization mechanism is elucidated based on the band diagram of materials.Results presented here are important to engineer high performance sensor devices by selecting the better work function of nanoparticles, depending on the Fermi level of semiconductor.

Wetting and Photocatalytic Behavior of Two-Dimensional Tin Oxides

Among the variety of two-dimensional oxides, tin oxides semiconducting are particularly interesting because of their promising in catalyst, energy harvesting, water purification, electronics device and space applications. In this study, three synthesized methods use adopted to explore the properties and application of oxides of tin sheets. The methods are air oxidation, aqueous and non-aqueous which characterized through techniques such as SEM-EDS, UV -spectroscopy, X ray diffraction, FTIR and photoluminescence. From SEM image showed the morphology of the tin oxide materials. The percentage of tin and oxygen from elemental analysis was ~ 55 % and 44 % respectively. FTIR spectra confirmed that Sn-O functional from the vibration peak. The X- ray diffraction pattern shows that prominent diffraction peak which indicates formation of tin oxide crystallinity. A photoabsorbtiy activity was tested in the tin oxide sample with methylene blue to explore how the tin oxide surface featured absorbs the integrity of a dye. Porosity and a surface alteration resulted in a increase in photoactivity. The tin oxide sheets emit green fluorescence in the UV light and emission might be dependent on the number of layers and concentration of it. The water droplet contact angle measure on the tin oxide sheets which is experimentally observed 69°. The theoretically molecular dynamics-based contact angle measurement was also studied on monolayer of stannous oxide, stannic oxide with effect of substrate. Based on above results, this material can be utilized as a photo-catalyst, drug delivery and thin film application of solar cell.

Preparation of SnO Nanoshells with Enhanced Lithium-Storage Properties.

Tin monoxide is a kind of IV-VI metal monoxides that has attracted great deal of attention due to its wide optical band gap and high field effect mobility in the past decade. On the other hand, nanoshell is a unique porous structure. Its curved shell provides a shelter for the hollow core, as well as a much bigger special surface area. We in this study systematically prepared SnO nanoshells through a facile self-assembly method under different annealing conditions. The lithium ion batteries were fabricated immediately based on the as prepared nanoshells. The capacity of as fabricated lithium ion batteries was 559.3 mAhg-1 at rate performance of 0.1 Ag-1 and 497.5 mAhg-1 at 1 Ag-1 in 30th cycle. This work exhibited high application performance of SnO nanoshells. We hope this work will help study similar structure and applications of IV-VI metal monoxides.

Structure and magnetic properties of Cr-Doped tin monoxide prepared by hydrothermal method

Ball- and sheet-like Sn1-xCrxO were successfully prepared by one-step hydrothermal method. The SEM and TEM results show that the diameter of ball-like unit is about 15 μm and the unit was assembled by several nanosheets with a thickness of about 0.5 μm. Raman pattern displays that there are two intense Raman mode Eg (~114 cm−1) and A1g (~211 cm−1) in the SnO, and the A1g peak shifted significantly. UV–Visible spectrum illustrates that the bandgap of the Cr-doped SnO firstly decreases and then increases as the Cr concentration increases, which is attributed to the sp-d exchange interactions and Burstein-Moss theory. The analysis of XPS also provides evidence for the incorporation of Cr into the system. Furthermore, it is found that oxygen vacancy (VO) decreases with the increase of Cr content. Based on Krӧger-Vink notation system, the competition mechanism between VO and VSn could explain the origin and variation of magnetism of Sn1-xCrxO from structural defects.

Formation of SnO and SnO2 phases during the annealing of SnO(x) films obtained by molecular beam epitaxy

SnO and SnO2 films were obtained on the SiO2 surface by the molecular-beam epitaxy method. The initial films are in the polycrystalline phase. The annealing of SnO(x) films at a temperature of 300 °C resulted in the formation of the tetragonal SnO phase. Three vibration modes Eg, A1g, and B1g with the frequencies of SnO bond vibrations of 113, 211 and ~360 cm−1, respectively, which correspond to the SnO phase, were first observed by the Raman spectroscopy method. The orthorhombic SnO2 films were obtained by increasing the annealing temperature to 500 °C. Based on the valence band XPS (X-ray photoelectron spectroscopy) spectrum, several features with the binding energy approximately 5 eV, 7.5 eV and 11 eV, which are the same with the valence band of SnO2, were identified. The refractive index and absorption coefficient were investigated by the spectral ellipsometry technique. The high absorption coefficients correspond to the high Sn content. The film dielectric properties were revealed at the temperature higher than 300 °C. The refractive index values lie in the range of 1.5–2.6 for the visible spectral region. The pronounced absorption edges at 2.85 eV and 3.6 eV corresponding to those of stannous oxide (SnO) and stannic oxide (SnO2) were observed. The photoluminescence (PL) from the SnO(x) films was observed at room temperature. The increase of the annealing temperature resulted in the increase of PL intensity. Such PL intensity behavior is likely due to the Sn nanoislands.

Growth of Less than 20 nm SnO Nanowires Using an Anodic Aluminum Oxide Template for Gas Sensing.

Stannous oxide (SnO) nanowires were synthesized by a template and catalyst-free thermal oxidation process. After annealing a Sn nanowires-embedded anodic aluminum oxide (AAO) template in air, we obtained a large amount of SnO nanowires. SnO nanowires were first prepared by electrochemical deposition and an oxidization method based on an AAO template. The preparation of SnO nanowires used aluminum sheet (purity 99.999%) and then a two-step anodization procedure to obtain a raw alumina mold. Finally, transparent alumina molds (AAO template) were obtained by reaming, soaking with phosphoric acid for 20 min, and a stripping process. We got a pore size of < 20 nm on the transparent alumina mold. In order to meet electroplating needs, we produced a platinum film on the bottom surface of the AAO template by using a sputtering method as the electrode of electroplating deposition. The structure was characterized by X-ray diffraction (XRD). High resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) with X-ray energy dispersive spectrometer (EDS) were used to observe the morphology. The EDS spectrum showed that components of the materials were Sn and O. FE-SEM results showed the synthesized SnO nanowires have an approximate length of ~10–20 μm with a highly aspect ratio of > 500. SnO nanowires with a Sn/O atomic ratio of ~1:1 were observed from EDS. The crystal structure of SnO nanowires showed that all the peaks within the spectrum lead to SnO with a tetragonal structure. This study may lead to the use of the 1D structure nanowires into electronic nanodevices and/or sensors, thus leading to nano-based functional structures.

Nonstoichiometric tin oxide films: study by X-ray diffraction, Raman scattering and electron paramagnetic resonance

Nonstoichiometric SnO/SnO2/SnO2−δ films were fabricated by DC magnetron sputtering and reactive DC magnetron sputtering of tin target with further 2-stage temperature annealing of synthesized materials. X-ray diffraction analysis, Raman spectroscopy and electron paramagnetic resonance (EPR) spectroscopy were employed to study the influence of oxygen content in the plasma during the sputtering process and the temperature of annealing on the stoichiometric and phase composition of synthesized films. It was found that the tin monoxide phase prevailed in the films fabricated by DC magnetron sputtering in the argon plasma followed by a 2-stage annealing process. Nanocrystalline films containing both tin monoxide and tin dioxide were synthesized when reactive magnetron sputtering with a small content of oxygen (of about 1 vol.%) was used. The increase of oxygen content in the plasma to the value of about 2 vol.% leads to the formation of amorphous films. The intensity of the Raman peaks inherent in SnO2 vibration modes was found to depend on the content of the tin monoxide phase in the films. This effect can be attributed to the dissipative transition of electronic excitation from tin monoxide to tin dioxide nanocrystallites.

Sol–gel synthesis of large-sized polycrystalline stannous oxide and its oxidation behavior

The large-sized polycrystalline stannous oxide (SnO) synthesized by a sol–gel method was found to have attractive crystal structural properties and thermo-oxidative stability.

Improved switching characteristics of p-type tin monoxide field-effect transistors through Schottky energy barrier engineering

Metal–interlayer–semiconductor contact reduces metal-induced gap states, mitigating Fermi-level pinning at metal/semiconductor interface. Here, switching property of p-type SnO FET is enhanced by increasing electron Schottky barrier at off-state.

Effect of Mechanical Strain on Electrical Performance of Flexible P-Type SnO Thin-Film Transistors

This article investigates the effect of mechanical bending strain on the electrical performance and gate-bias stability of flexible p-type tin monoxide (SnO) thin-film transistors (TFTs). The on-polyimide SnO TFTs have an inverted-staggered structure with a back channel passivated by SiN x and HfO2 layers. The as-fabricated linear field-effect mobility, threshold voltage, subthreshold swing, and ON/OFF current ratio are 0.41 cm $^{{2}}\text{V}^{-{1}}\text{s}^{-{1}}$ , 0.74 V, 1.9 V/dec, and $1.1\times 10^{{4}}$ , respectively. The field-effect mobility decreases as the applied tensile strain increases, while it stays almost unaltered when a compressive strain is applied. A prominent increase of the positive-gate-bias-stress-induced threshold voltage shift is observed when the TFT is outwardly bent. The result shows that the mechanical tensile strain has a more significant impact on the electrical performance of p-type SnO TFTs.

Oxide Thin-Film Transistor-Based Vertically Stacked Complementary Inverter for Logic and Photo-Sensor Operations.

Numerous studies have addressed the utilization of oxide thin-film transistor (TFT)-based complementary logic circuits that are based on two-dimensional (2D) planar structures. However, there are fundamental limits to the 2D planar structured complementary logic circuits, such as a large dimension and a large parasitic resistance. This work demonstrated a vertically stacked three-dimensional complementary inverter composed of a p-channel tin monoxide (SnO) TFT and an n-channel indium-gallium-zinc oxide (IGZO) TFT. A bottom-gate p-channel SnO TFT was formed on the top-gate n-channel IGZO TFT with a shared common gate electrode. The fabricated vertically stacked complementary inverter exhibited full swing characteristics with a voltage gain of ~33.6, a high noise margin of 3.13 V, and a low noise margin of 3.16 V at a supplied voltage of 10 V. The achieved voltage gain of the fabricated complementary inverter was higher than that of the vertically stacked complementary inverters composed of other oxide TFTs in previous works. In addition, we showed that the vertically stacked complementary inverter exhibited excellent visible-light photoresponse. This indicates that the oxide TFT-based vertically stacked complementary inverter can be used as a sensitive photo-sensor operating in the visible spectral range with the voltage read-out scheme.

Lanthanum Doping Enabling High Drain Current Modulation in a p-Type Tin Monoxide Thin-Film Transistor.

Effects of lanthanum (La) loading on the structural, optical, and electrical properties of tin monoxide (SnO) films were examined as a p-type semiconducting layer. La loading up to 1.9 atom % caused the texturing of the tetragonal SnO phase with a preferential orientation of (101), which was accompanied by the smoother surface morphology. Simultaneously, the incorporated La cation suppressed the formation of n-type SnO2 in the La-doped SnO film and widened its optical band gap. These variations allowed the 1.9 atom % La-loaded SnO film to have a high hole mobility and carrier density, compared with the La-free control SnO film. The superior semiconducting property was reflected in the p-type thin-film transistor (TFT). The control SnO TFTs exhibited the field-effect mobility (μSAT) and ION/OFF ratio of 0.29 cm2 V-1 s-1 and 5.4 × 102, respectively. Enhancement in the μSAT value and ION/OFF ratio was observed for the TFTs with the 1.9 atom % La-loaded SnO channel layer: they were improved to 1.2 cm2 V-1 s-1 and 7.3 × 103, respectively. The reason for this superior performance was discussed on the basis of smoother morphology, suppression of disproportionation conversion from Sn2+ to Sn + Sn4+, and reduced gap-state density.

Effects of substrate temperature on characteristics of the p-type Ag-doped SnOx thin films prepared by reactive DC magnetron sputtering

P-type transparent conductive oxides are one of long-persued research topics in scientific community. Substitutes for unstable p-type zinc oxide are in urgent need than ever and doped tin monoxide can be a material-of-choice. In this report, we present Ag-doped SnOx thin film produced by reactive DC magnetron sputtering from Sn + Ag alloy targets. We investigated and proved the strong influence of substrate temperatures on crystal structure, optical and electrical properties. Tin monoxide thin films showed tetragonal crystal structure and preferred diffraction peaks of (001), (101), (110), (002). As substrate temperature increased, grain size also increased, leading to reduced grain boudaries, higher hole mobility and lower resistivity. Films deposited at low (150 °C) and high (300 °C) substrate temperatures had the presence of exotic β-Sn and SnO2 phases, respectively.They acted as undesired scattering centers or induce harmful carrier recombination which decreased mobility or hole concentration. The Ag-doped SnO films fabricated at 250 °C had the best electrical properties, hole concentration 5.82 × 1018 cm−3, mobility 4.1 cm2/Vs, resistivity 2.262 × 10-1Ωcm. Current-voltage characteristics of thin film diode structures of glass/FTO/n-nc-Si:H /p-Ag:SnO/Cu and glass /FTO/n-nc-Si:H /undoped SnO/Cu were studied. They showed remarkably improved electric properties of SnO: Ag films compared to the pristine SnO counterpart.

High-Gain Complementary Inverter Based on Corbino p-Type Tin Monoxide and n-Type Indium-Gallium-Zinc Oxide Thin-Film Transistors

The present work investigated the electrical characteristics of Corbino structure p-type tin monoxide (SnO) thin-film transistors (TFTs) and demonstrated a high-performance complementary logic inverter composed of Corbino p-type SnO and n-type indium-gallium-zinc oxide (IGZO) TFTs. Experimental data showed that the Corbino p-type SnO TFT exhibited an almost infinite output resistance beyond pinch-off in the outer drain condition. The observed phenomenon was mainly attributed to the scaling down of the effective channel width in proportion to the effective channel length. By using the very high output resistance of the Corbino structure TFTs, we fabricated the high-gain complementary logic inverter composed of Corbino p-type SnO and n-type IGZO TFTs. The Corbino TFT-based complementary logic inverter showed a voltage gain of 92.4 at a supplied voltage of 10 V, which was significantly higher than that of 18.7 obtained from the complementary logic inverter composed of the conventional rectangular shaped TFTs.

Facilely transforming bulk materials to SnO/pristine graphene 2D-2D heterostructures for stable and fast lithium storage

Two-dimensional (2D) nano-structured tin monoxide (SnO) offers fascinating possibilities as anode material for lithium ion batteries (LIBs). 2D architectures of SnO are highly desirable to access advanced lithium storage properties however their application is impeded by the lack of synthetic method. In this study, we report a scalable synthetic route to facilely deriving SnO/pristine-graphene (p-G) 2D-2D heterostructure from bulk SnO and graphite. A “top-down” synthetic method was found effective in transforming SnO micro-sized particles into nanosheets down to a few nanometers in thickness. Assembled with pristine graphene (p-G), the SnO nanosheets were used to build a SnO/p-G heterostructure that delivers remarkable Li-ion storage performances: reversible capacities of 633.9 mAh g−1 after 100 cycles at 0.05 A g−1, and excellent cycling stabilities (0.027% capacity fade per cycle at 1 A g−1 after 700 cycles) were obtained. In comparison, raw SnO exhibited severe SEI over-growth and continuous capacity decay from the on-set at 0.05 A g−1. The structural advantages of 2D-2D heterostructure were elucidated to understand its exceptional lithium storage properties. This study demonstrates a facile and scalable strategy for producing 2D-2D heterostructures from low-cost bulk materials for LIBs application.

Investigation of electronic and chemical sensitization effects promoted by Pt and Pd nanoparticles on single-crystalline SnO nanobelt-based gas sensors

This work reports on the gas sensor response of undecorated 1D stannous oxide nanobelts and those decorated with Pt and Pd nanoparticles. The sensor device responses to H2, CO and NO2 were measured in dry air baseline atmosphere as functions of the analyte concentration (1–1000 ppm) and temperature (100-350 °C). Noble metal decorated SnO devices exhibited enhanced chemical sensitization, resulting in increased sensitivity upon exposure to reducing gases at different working temperatures. Differences in enhancement levels are attributed to strong electronic sensitization effects that are dependent on the respective Pt and Pd work functions and the unique SnO band structure, characterized by a small band gap. Gas sensing results also showed superior selectivity to H2 for metal-decorated nanobelts. Based on the findings in this work, we propose an array based on SnO structures capable of detecting and distinguishing reducing and oxidizing gases.

Surface engineering of layered SnO micro-plates for impressive high supercapacitor performance

Tin monoxide is an important functional material, which is widely used in energy storage and optoelectronic devices. In this work, SnO micro-plates were synthesized by low-temperature hydrothermal method using aqueous ammonia as reducing agent. The thickness and surface morphology of the SnO micro-plates were delicately controlled by adjusting ammonia concentration. It is shown that surface modification has significant effect on their supercapacitor performance. Specifically, an ultra-high specific capacity of 1080 F•g−1 is obtained, which reaches ~75% of its theoretical faradaic capacitance value. Considering the typical thickness of ~250 nm, the electrons/ions can diffuse ~90 nm into the sample. In addition, the capacity remains an impressive value of 849 F•g−1 after 1000 cycles at current density of 1 A•g−1, suggesting excellent stability. Our studies show that the non-transition metal oxide, SnO, is a promising supercapacitor electrode material with high specific capacity and good cycle stability.

SnO@amorphous TiO2core-shell composite for advanced lithium storage

Abstract Tin monoxide(SnO) has been considered as a promising candidate for the next-generation lithium storage due to its exceptional specific capacity and unique layered structure. However, the huge volume change of SnO during lithiation/delithiation process tends to cause various mechanical failure problems including the delamination between the current collector and the electrode materials, leading to poor stability of the lithium-ion batteries. Herein we propose to solve the interfacial delamination problem by encapsulating the SnO microspheres in amorphous TiO 2 . The prepared SnO@amorphous TiO 2 core-shell composite is found quite successful in alleviating the interfacial delamination, resulting in higher capacity retention and faster solid-state ion diffusion. Specifically, the SnO@amorphous TiO 2 core-shell composites electrode shows a stable charge capacity of 253.6 mAh g -1 after 200 cycles, which is much higher than that of the pure SnO electrode (141.1 mAh g -1 ). Our work provides a guideline for the design and manufacture of the SnO-based electrodes for LIBs.

Effects of layer stacking and strain on electronic transport in two-dimensional tin monoxide**Project supported by the National Natural Science Foundation of China (Grant No. 11747054), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 2018M631760), the Project of Hebei Educational Department, China (Grant Nos. ZD2018015 and QN2018012), and the Advanced Postdoctoral Programs of Hebei

Tin monoxide (SnO) is an interesting two-dimensional material because it is a rare oxide semiconductor with bipolar conductivity. However, the lower room temperature mobility limits the applications of SnO in the future. Thus, we systematically investigate the effects of different layer structures and strains on the electron–phonon coupling and phonon-limited mobility of SnO. The A2u phonon mode in the high-frequency region is the main contributor to the coupling with electrons for different layer structures. Moreover, the orbital hybridization of Sn atoms existing only in the bilayer structure changes the conduction band edge and conspicuously decreases the electron–phonon coupling, and thus the electronic transport performance of the bilayer is superior to that of other layers. In addition, the compressive strain of ε = −1.0% in the monolayer structure results in a conduction band minimum (CBM) consisting of two valleys at the Γ point and along the M–Γ line, and also leads to the intervalley electronic scattering assisted by the mode. However, the electron–phonon coupling regionally transferring from high frequency A2u to low frequency results in little change of mobility.

Divalent Path to Enhance p-Type Conductivity in a SnO Transparent Semiconductor

The role of the divalent nature of tin is explored in tin monoxide, revealing a novel path for enhancing p-type conductivity. The consequences of oxygen off-stoichiometry indicate that a defect com...