Tin Oxide Semiconductor Research Articles

Study of Gas Sensors for the Detection of Volatile Organic Compounds in Breath

Volatile organic compounds (VOCs) are organic chemicals that encompass a high vapour pressure .The VOCs are numerous and varied. In breath the concentration of VOCs ranges from parts per million to parts per trillion. The discovery of VOCs in breath is used as a diagnostic tool for many diseases, disorders and metabolic studies. So far these gases have been identified using gas chromatography (GC) which is time consuming and expensive technique. With the introduction of sensors as frontend to detect vapour signals, the work can be processed easier. This article proposes a system for breath analysis using tin oxide semiconductor gas sensors, in which the conductivity changes depending on the concentration of the vapour. A prototype model was developed to detect the presence of acetone in the breath, which is a biomarker for diabetes mellitus. This study has been helpful in designing an electronic nose for detecting other vapours like benzene, ammonia and Nitric oxide which are the biomarkers for lung cancer, renal disorder and asthmatic inflammation.

High Mobility and Stability of Thin-Film Transistors Using Silicon-Doped Amorphous Indium Tin Oxide Semiconductors

We report the fabrication of high-performance thin-film transistors (TFTs) with an amorphous silicon indium tin oxide (a-SITO) channel, which was deposited by cosputtering a silicon dioxide and an indium tin oxide target. The effect of the silicon doping on the device performance and stability of the a-SITO TFTs was investigated. The field-effect mobility and stability under positive bias stress of the a-SITO TFTs with optimized Si content (0.22 at.% Si) dramatically improved to 28.7 cm2/Vs and 1.5 V shift of threshold voltage, respectively, compared with the values (0.72 cm2/Vs and 8.9 V shift) for a-SITO TFTs with 4.22 at.% Si. The role of silicon in a-SITO TFTs is discussed based on various physical and chemical analyses, including x-ray absorption spectroscopy, x-ray photoelectron spectroscopy, and spectroscopic ellipsometry measurements.

Thin film complementary metal oxide semiconductor (CMOS) device using a single-step deposition of the channel layer.

We report, for the first time, the use of a single step deposition of semiconductor channel layer to simultaneously achieve both n- and p-type transport in transparent oxide thin film transistors (TFTs). This effect is achieved by controlling the concentration of hydroxyl groups (OH-groups) in the underlying gate dielectrics. The semiconducting tin oxide layer was deposited at room temperature, and the maximum device fabrication temperature was 350°C. Both n and p-type TFTs showed fairly comparable performance. A functional CMOS inverter was fabricated using this novel scheme, indicating the potential use of our approach for various practical applications.

Photoelectrochemical Competitive Detection of Biotin

Abstract Quantitative detection of small molecules by a photoelectrochemical system was demonstrated in a competitive assay for biotin. The system for the determination of Biotin was employed by using ruthenium tris(bipyridine) (Ru-bpy) as the label, oxalate as the sacrificial electron donor to recycle the label, and tin oxide nanoparticle as the semiconductor electrode. Upon irradiation with 470 nm light, electrons of Ru-bpy were promoted to the excited state, and then injected into the conduction band of the tin oxide semiconductor, thus producing photocurrent signal. The oxidized Ru-bpy was reduced back to its original state by oxalate in solution, and was used again in the next cycle of signal generation. In the competitive assay of biotin, avidin was adsorbed passively on the tin oxide surface as the recognition element. Adsorbed protein was found to be stable under assay conditions, and reached maximum surface coverage when the concentration of avidin solution for adsorption was 0.5 g L −1 or higher. A mixed solution of 1 μM tracer and various concentrations of biotins were reacted with surface-immobilized avidin. As biotin concentration was increased, less tracer molecules bound to avidin, leading to a reduction in its photocurrent signal. A detection limit of 8 μg L −1 biotin was obtained in the competitive assay. The method can be easily extended to the detection of competitive immunoassays for organic chemicals.

Quantitative Recognizing Dissolved Hydrocarbons with Genetic Algorithm-Support Vector Regression

Online monitoring of dissolved fault characteristic hydrocarbon gases, such as methane, ethane, ethylene and acetylene in power transformer oil has significant meaning for condition assessment of transformer. Recently, semiconductor tin oxide based gas sensor array has been widely applied in online monitoring apparatus, while cross sensitivity of the gas sensor array is inevitable due to same compositions and similar structures among the four hydrocarbon gases. Based on support vector regression (SVR) with genetic algorithm (GA), a new pattern recognition method was proposed to reduce the cross sensitivity of the gas sensor array and further quantitatively recognize the concentration of dissolved hydrocarbon gases. The experimental data from a certain online monitoring device in China is used to illustrate the performance of the proposed GA-SVR model. Experimental results indicate that the GA-SVR method can effectively decrease the cross sensitivity and the regressed data is much more closed to the real values. DOI: http://dx.doi.org/10.11591/telkomnika.v11i9.2776

Recent research situation in tin dioxide nanomaterials: synthesis, microstructures, and properties

This review article summarizes the new research in solid-state physical chemistry understanding of the microstructure characteristics of semiconductor tin oxide thin films made in the last years in our group. The work mainly focuses on the fabrication technology of semiconductor tin oxides thin films by using pulsed laser deposition (PLD) as well as the application of this technology on new micro- and nanostructured materials. It is an interdisciplinary work that integrates the areas of physics, chemistry and materials science.

UV–Visible Spectroscopic Analysis of Electrical Properties in Alkali Metal‐Doped Amorphous Zinc Tin Oxide Thin‐Film Transistors

Solution-processed and alkali metals, such as Li and Na, are introduced in doped amorphous zinc tin oxide (ZTO) semiconductor TFTs, which show better electrical performance, such as improved field effect mobility, than intrinsic amorphous ZTO semiconductor TFTs. Furthermore, by using spectroscopic UV-visible analysis we propose a comprehensive technique for monitoring the improved electrical performance induced by alkali metal doping in terms of the change in optical properties. The change in the optical bandgap supported by the Burstein-Moss theory could successfully show a mobility increase that is related to interstitial doping of alkali metal in ZTO semiconductors.

Gas reception and signal transduction of neat tin oxide semiconductor sensor for response to oxygen

The basic schemes of gas reception and signal transduction recently proposed for oxide semiconductor gas sensors have been shown to apply well to the quantitative analysis of the oxygen response behavior observed with a neat SnO2 sensor under various humidity conditions at 623K. It was shown that O2− ions are preferably formed under a very dry condition but their formation is strongly suppressed in the presence of slight amounts of moisture through blocking of adsorption sites and induction of threshold pressure, and is replaced by the formation of O− ions. To make the situation more complex, the formation of these ions was increasingly enhanced with increasing humidity of pretreatment ambient at elevated temperature (hysteresis), which is considered to result from surface restructuring having taken place in the pretreatments. Through these results, chemical properties and stabilities of grain surface, beside physical properties of the grains, were shown to be critically important for gas sensing properties.

Detection of Metabolic Gas Emitted by Termites Using Semiconductor Gas Sensors

ABSTRACT The feasibility of using three types of semiconductor gas sensors to detect the metabolic gas generated by termites was investigated. Odor, methane, and hydrogen sensors made of a tin oxide semiconductor were tested. A polypropylene container was prepared with three sensors in the lid to investigate the relationship between the number of termites and food material on gas concentration over time. Worker and soldier termites (Coptotermes formosanus), collected from a laboratory colony, were put into the container with and without food material (wood specimen). The variation in the electrical resistance of the sensors during the detection of gas components was monitored, and the detected voltage was converted into gas concentration. The hydrogen concentration increased with an increase in the number of termites and was not influenced by gases released from the wood specimen. Similar findings were obtained for the odor sensor, even though it detected odor components from both termites and the wood specimen. The methane sensor did not detect any significant increase in gas concentration. The results showed that the hydrogen emission depended on the feeding activity of worker termites, whereas soldier termites that were supplied with food material by worker termites made a small contribution to hydrogen emission. These findings suggest that because of the high selectivity and sensitivity of the hydrogen sensor, its performance is better than that of the odor and methane sensors for the detection of termite attacks.

Ultrahigh-gain single SnO2 nanowire photodetectors made with ferromagnetic nickel electrodes

We report the first attempt at magnetic manipulation of the photoresponse in a one-dimensional device in which a highly sensitive ultraviolet photodetector, composed of tin dioxide nanowire (SnO2 NW) and ferromagnetic nickel (Ni) electrodes, has been fabricated and characterized. Surprisingly, as the Ni electrodes were magnetized, the photocurrent gain was greatly enhanced by up to 20 times, which is far beyond all of the previously reported enhancement factors for functionalized NW photodetectors. The underlying mechanism enabling the enhanced gain is attributed to both oxygen molecules adsorbed and surface band-bending effects due to the migration of electrons to the surface of SnO2 NW caused by the magnetic field of ferromagnetic electrodes. The novel approach presented here can provide a new route for the creation of highly efficient optoelectronic devices based on the coupling between ferromagnetic materials and nanostructured semiconductors. Yang-Fang Chen and co-workers from the National Taiwan University have dramatically enhanced the photoresponse of tin oxide semiconductor nanowires using a magnetic field. Tin oxide nanowires can produce a photocurrent under irradiation through the separation of electron–hole pairs at an irradiated location — an effect that makes the nanowires attractive components for a variety of devices including gas sensors and solar cells. The photoresponse depends on the nanowires' morphology, the presence of other ‘dopant’ species, and can be typically tuned through an electric field. The researchers have now devised a system in which the photocurrent can be amplified — by up to 20 times — using a magnetic field instead. A tin oxide nanowire is placed between two nickel ‘ferromagnetic’ electrodes and the resulting device subjected to a magnetic field. The high photoresponse observed is attributed to a migration of electrons towards the surface of the nanowires, induced by the electrodes' magnetization. This combination of nanowires with ferromagnetic materials may serve in future to fabricate efficient optoelectronic devices. We report the first attempt of magnetic manipulation of photoresponse in an one-dimensional device, in which a highly sensitive photodetector in the UV region composed of tin oxide nanowire and ferromagnetic nickel electrodes have been fabricated and characterized. Surprisingly, as the Nickel electrodes were magnetized, the photocurrent gain can be greatly enhanced by up to 20 times. The underlying mechanism is attributed to both oxygen molecules adsorbed and surface band bending effects due to the migration of electrons to the surface of tin oxide nanowire caused by the magnetic field of ferromagnetic electrodes.

Characterization of amorphous zinc tin oxide semiconductors

Abstract

Solid‐State Electrochemiluminescence of F‐doped SnO2 Nanocrystals and Its Sensing Application

AbstractElectrochemiluminescence (ECL) behaviors and mechanisms of fluorine‐doped tin oxide (F‐SnO2) semiconductor nanocrystals (NCs) were firstly investigated in both of nonaqueous and aqueous solutions via potential scanning or pulsing. Furthermore, the ECL of F‐SnO2 was applied successfully to detect dopamine based on the quenching effect.

Solution processed IZTO thin film transistor on silicon nitride dielectric layer

Solution process-based inorganic indium–zinc–tin oxide semiconductor layer was applied to fabricate a thin film transistor (TFT) by annealing at 600 °C on plasma enhanced chemical vapor deposited (PECVD) silicon nitride (SiN x ) dielectric layer. The spin-coated indium–zinc–tin oxide (IZTO) transistor has a field-effect mobility of 4.36 cm 2/V s with on/off ratio of 10 5 having the subthreshold voltage shift of 0.537 V/dec. The device characterization and surface analysis after annealing were performed and compared with results before annealing. Our results offer the feasibility of solution-based oxide semiconductor transistors for cost-effective display or other electronic devices.

Solution-Processed Oxide Thin Film Transistors with Indium Zinc Tin Oxide Semiconductor: Nitrogen Effect

Thin film transistors (TFTs) with nitrogen incorporated indium zinc tin oxide (IZTO:N) channel layer were fabricated and characterized. For the IZTO:N channel, TFTs was fabricated on heavily doped Si as a common gate electrode and silicon nitride (SiNx) was used as a gate dielectric layer. The IZTO:N layer was formed by spin-coating as precursor type solution and annealed at 600C. The precursors for indium, zinc, and tin were indium chloride, zinc chloride, and tin chloride. The incorporation of nitrogen was accomplished by addition of NH4OH solution. The IZTO:N TFT prepared with the precursor solution having 0.7% NH4OH has show the performance in mobility 1.2cm2/Vs, Ion/off of 10^6 and threshold voltage of 8.5V.

Solution-Processed Oxide Thin Film Transistors with Indium Zinc Tin Oxide Semiconductor: Nitrogen Effect

not Available.

Vanadium-promoted tin oxide semiconductor carbon monoxide gas sensors

The semiconductor gas sensors investigated are constituted by vanadium-tin oxide nanoparticles, prepared by a co-precipitation method. They were evaluated for carbon monoxide detection at low temperatures. The sensing characteristics obtained are associated with the composition, structure and surface state of oxide semiconductor. XPS analysis revealed an electronic interaction between Sn and V atoms in the mixed oxide structure and the formation of vanadium cations with multiple valences. Combined XRD and FTIR analyses showed that the tin oxide crystallinity decreased with increasing vanadium loadings. Lower levels of vanadium dopants in tin oxide enhanced response to CO gas in air because they facilitated oxygen adsorption by scavenging electrons to form reactive oxygen ions on the surface, as indicated by electrical and EPR measurements. The response to CO gas in nitrogen atmosphere was observed, and increased with increasing CO concentrations. Sensing mechanisms that discuss the roles of the vanadium redox pairs and oxygen vacancies in the CO detection process are proposed.

Characterization of SnO2:F thin films deposited by an economic spray pyrolysis technique

AbstractFluorine doped tin oxide (FTO) semiconductor thin films were deposited on glass substrates using spray pyrolysis technique and the effect of fluorine (F‐) doping (varying 0‐30 at%) is explored. X‐ray diffraction studies confirmed the tetragonal structure with polycrystalline nature. The crystallinity of undoped films is enhanced with the increase in F‐doping. The films doped with 25 at% F show a strong orientation along (101) plane. The grain size of the undoped films (214 nm) is increased with the increase in F‐doping level to reach a maximum of 415 nm (25 at% F). A minimum sheet resistance of ∼5.4 Ω/□ obtained for the 30 at% F doped films is among the lowest reported values. The average visible transmittance (400‐700 nm) of the undoped films (61.4%) is increased with the increasing F‐doping to reach a maximum of 74.5% (25 at%. F). The films doped with 25 at.% F showed high value of figure of merit (4.55 × 10‐3 Ω‐1). The obtained results authenticate the influence of F‐doping on the properties of the deposited films. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation and characterization of p-type semiconducting tin oxide thin film gas sensors

P-type conducting undoped tin oxide thin film gas sensor is fabricated by direct current reactive magnetron sputtering method and calcination technique. Physical characteristics of the undoped tin oxide thin films have been analyzed by Spectroscopic ellipsometer, x-ray diffraction (XRD), scanning electronic microscope, and atomic force microscopy. According to the ethanol sensitivity properties of the sensors, we find that the calcination temperature and the thickness of the films are correlated with the special p-type conducting type; the p-type ultrathin film (10 nm) gas sensor shows better gas sensitivity and less baseline shift. XRD studies indicate that the preferred unidentified diffraction peak at 33.082° favors the formation of p-type conducting. When the intensities of unidentified diffraction peak increases, the gas sensing properties is largely promoted. The response time of the p-type sensor is less than 1 s to 1000 ppm ethanol.

Energy level evolution of molybdenum trioxide interlayer between indium tin oxide and organic semiconductor

The thickness dependance of molybdenum trioxide (MoO3) interlayer between conducting indium tin oxide (ITO) and chloro-aluminum pthalocyanine (AlPc-Cl) has been investigated with ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy. It was found that the MoO3 interlayer substantially increased the surface workfunction (WF). The increase was observed to saturate at 20 Å of MoO3 coverage. The increased WF results in hole accumulation and a band-bendinglike situation in the subsequently deposited AlPc-Cl. From these observations, a possible explanation is deduced for the observed reduction in series resistance by the insertion of the MoO3 insulating layer.

Evidence by EIS of the interaction between proteins and tin oxide electrode surface

Macromolecules like proteins are able to adhere to tin oxide electrodes at open circuit potential as proved by electrogravimetry experiments. In this work, electrochemical impedance studies were performed at aqueous electrolyte/F- or Sb-doped semiconducting tin oxide interfaces, including natural seawater. By this way, it was possible to characterize the potential dependence of the interfacial capacitance in various physicochemical conditions, without or in the presence of bovine serum albumin (BSA). In the potential range where tin oxide is in the depletion regime (blocking interface), a capacitance excess is evidenced which can be attributed to the formation of surface states which are the signature of chemical bonding. By simulating the so-called surface state capacitance, three states have been pointed out. They are centred at 0.7, 0.9 and 1.1 eV in the tin oxide bandgap. On the basis of experimental arguments, the state at 1.1 eV was ascribed to the OH-terminated tin oxide surface, the two other states were found to be specific of the interaction of organic matter with the oxide surface. In the presence of BSA, the density of surface atoms (about 10 13 cm −2) involved in bonding is of the order of magnitude of the surface concentration of one BSA monolayer. The lasting character of these bonds was also shown. This finding shows the definitive protein immobilisation at the SnO 2 surface.