SiO2 Wafer Research Articles

A Comparative Study of Structural Contribution to Biocidability via Immobilization of Fluorinated and Nonfluorinated Quaternary Ammonium Salts on Top Surfaces.

Higher biocidability of fluorinated quaternary ammonium salt (QAS) is usually contributed to its preferential segregation to the surface to better contact with and kill bacteria. However, whether its structure also elicits better performance is still unclear. Herein, the same amount of a fluorinated QAS and its nonfluorinated counterpart are both immobilized on the top surface to eliminate the effect of concentration distribution to only study their structure-biocidability relationship. Briefly, the fluorinated and nonfluorinated QASs were synthesized by quaternization of N,N-dimethylethanolamine with 2-(perfluorooctyl)ethyl bromide that was prepared by bromination of 2-(perfluorooctyl)ethanol and 1-bromodecane, respectively. Polystyrene (PS) and diblock copolymer poly(styrene)-b-poly(tert-butyl acrylate) (PS-PtBA) were successively spin coated on SiO2 wafers at different concentrations to form bilayer structures that have a PS base layer and a PtBA top layer. The tert-butyl acrylate groups of the PtBA layer of 0.9 nm were converted to carboxylic acid groups with trifluoroacetic acid for respective esterification with the two hydroxy-containing QASs. It was observed that the fluorinated and nonfluorinated surfaces fabricated at the maximum comparable esterification yield of 63.5% fully eradicated ∼104 CFU of Staphylococcus aureus and Escherichia coli in 120 and 150 min, respectively, indicating that the fluorocarbon chain is more biocidal through better interpenetration into bacterial membranes. Immobilization of a functionality on top surface provides a universal strategy to study its structural contribution to activity without interference of the concentration distribution.

High-Performance CsPbI3 Quantum Dot Photodetector with a Vertical Structure Based on the Frenkel-Poole Emission Effect.

The selection of photoactive materials and the design of device structures are critical to the photoelectronic performance of photodetectors. This study reports on a vertically structured photodetector device with rapid, stable, and efficient photoelectric performance across the UV-visible broadband range based on the Si++/SiO2/Au/single-layer graphene/CsPbI3 quantum dots (QDs) configuration. In this specific device structure, a relatively high conductivity Si++/SiO2 wafer was used as the substrate, a CsPbI3 QD film with high light absorption was used as the photoactive layer, and a monolayer graphene with high conductivity was inserted between the substrate and the CsPbI3 QD film to form a heterojunction with the QD film. Based on the Frenkel-Poole emission effect arising from the high trap state density within the SiO2 layer, the device exhibited excellent photoelectric performances. Especially at a wavelength of 365 nm, a photocurrent responsivity of 2319 A/W, a specific detectivity of 1.15 × 1014 Jones, an external quantum efficiency of 7883%, and an on/off time of 39/36 ms at a Si++ terminal voltage of -80 V and an optical power density of 84.03 nW/cm2 can be achieved.

Sensitive detection of low doses beta particles using quartz crystal oscillators

The demand for developing a cheap and novel ionizing radiation detection technique has recently increased. This work aims to establish a new detection method for beta particles based on a quartz tuning fork (QTF). QTF coated and uncoated with 40 nm of aluminum (Al) were used to evaluate the system under different conditions. All samples were exposed to different doses of beta using a 90Sr beta source. The results confirmed that a clear frequency shift was observed during beta irradiation. Once the radiation source was removed, the frequency returned to normal behavior. This effect is more pronounced with the Al-coated sample due to more tensile stress caused by thermal heating induced by beta radiation. Before and after beta irradiation, the optical properties of SiO2 wafers (quartz) were also studied using spectroscopic ellipsometry (SE) measurements. The SE results were largely consistent with the QTF resonance frequency shift results. In conclusion, experiment results proved the probability of using QTF as sensitive, accurate, and easy-to-use sensing for low-dose beta radiation.

Hydrophilic Bonding of SiO2/SiO2 and Cu/Cu using Sequential Plasma Activation

To meet the increasing market demand for next-generation electronic devices, 3D system integration is getting greater and greater attention. However, traditional methods such as soldering or bump bonding cannot handle high density interconnection. Therefore, hybrid bonding technology, which simultaneously bonds Cu wiring layer and SiO2 dielectric layer, is indispensable. In the hybrid bonding process, hydrophilic bonding is commonly used to bond SiO2 to SiO2. This technique involves bonding of hydrophilic bonding surfaces, followed by post-bonding annealing to achieve a reliable bonding interface. For Cu bonding, it is necessary to break the oxide layer at the Cu bonding interface and allow Cu atoms to diffuse into each other to achieve electrical connection.However, since post-bonding annealing at high temperatures can damage the device or induce residual stress at the bonding interface, low temperature process below 200°C is preferable. Currently, the most widely adopted process is hydrophilic bonding using N2 plasma, which also achieves hybrid bonding through heating at around 350°C to 400°C.In this study, we propose to apply sequential plasma activation bonding (SPAB), which has been shown to be effective for low-temperature bonding of quartz glass, to the bonding of TEOS SiO2 and Cu. SPAB is a technique that forms a highly reactive oxynitrides on the substrate by continuously irradiating the bonding surface with O2 plasma, N2 plasma, and nitrogen radicals. This then adsorbs a large amount of OH groups by reacting with moisture, leading to a strong bond after bonding and post-bonding annealing at 200°C. Since this technique is effective for quartz, it is expected to be effective for TEOS SiO2 as well, and we also investigate its effect on Cu in this study.For this, we investigated the effect of SPAB for blanket TEOS SiO2 and Cu wafer separately. Cu layers were deposited on 4 inch, 525 µm thick Si wafers, and TEOS SiO2 layers on 6 inch, 625 µm thick Si wafers. The Cu layers were deposited by sputtering with a 1 µm thickness, while the SiO2 layers were deposited using plasma-enhanced TEOS process for a 1 µm thickness. Both types of deposited layers were planarized by CMP.The SPAB process was carried out using RIE plasma and microwave radicals of N2 and O2 gas. The bonding surfaces were activated by O2 plasma, N2 plasma, and N radicals sequentially. After the surface activation, the wafers were exposed to ambient air to adsorb water on the surface, followed by bonding in air and post-bonding annealing at 200°C for 2 hours.For comparison, bonding was also carried out using only N2 plasma and only O2 plasma activation, respectively. Results show that when surface activation was performed using only N2 plasma, the bond strength was 0.75 J/m2 for TEOS SiO2 and 0.33 J/m2 for Cu. In the case of O2 plasma activation, the bond strength was 0.57 J/m2 for TEOS SiO2 and 0.98 J/m2 for Cu.On the other hand, the SPAB technique improves the bond strength to 1.13 J/m2 for TEOS SiO2 and 1.03 J/m2 for Cu. Therefore, it can be concluded that the SPAB technique enhances the bond strengths of both TEOS SiO2 and Cu compared to single gas plasma activation. Since the SPAB improves the bond strength of both SiO2 and Cu in the same process condition with annealing temperature of 200°C, this technique will contribute low temperature hybrid bonding applications.

Electrostatic Spray Deposition of Al-Doped ZnO Thin Films for Acetone Gas Detection

In this study, pure ZnO and Al-doped ZnO(AZO) thin films were coated onto a SiO2 wafer using the electrostatic spray deposition (ESD) process for acetone gas detection under laboratory conditions. Voltage levels were varied to determine the optimal conditions for producing thin films with the highest uniformity. The results indicate that the optimal coating voltage for achieving the highest uniformity of the coated films is 2.9 kV for ZnO and 2.6 kV for AZO. The thin films were produced under these optimal ESD conditions by adjusting the coating time, and gas sensors were fabricated by printing electrodes using a reverse offset process on top of the thin films. Analysis of the sensing response revealed that the AZO-coated gas sensor with a 200 s deposition exhibited the best acetone-sensing ability at 300 °C, with a maximum response of 13.41 at 10 ppm. Furthermore, the fabricated gas sensors effectively detected acetone gas even at a low concentration of 2 ppm, demonstrating high selectivity in comparison to other gases.

Real-time monitoring of liquid–solid phase transition by using an ion-beam-synthesized Au/SiO2 nanocomposite refractive index sensitive element

Au/SiO2 nanocomposite refractive index sensitive element was prepared by implanting 30 keV Au ions into a 0.5-mm-thick SiO2 wafer at a fluence of 4.5 × 1016 ions/cm2. Combining this sensitive element with other components, a device was built to measure the reflection spectra of water and 4 % brine in real time during the cooling courses. With the recorded characteristic reflection peaks’ positions, two media’s refractive indices were calculated, and their phase transition processes were discussed. The results revealed that the water–ice phase transition in the cooled water was a very fast process, and the water freezing and the progressive salt precipitation existed in the cooled brine. These satisfactory and reproducible results demonstrated that the ion-beam-synthesized Au/SiO2 nanocomposite refractive index sensitive element was quite stable in structure, and thus, it could find its niche in the fields of selecting phase transition materials, preserving biological cells, and desalinating frozen seawater, etc.

Modelling and Optimization of the Differential Surface Capacitance in Electrolyte-Gated Graphene Field-Effect Transistors

Graphene field-effect transistors (GFETs) are a promising avenue for the detection of biomarkers, allowing to envision improvements in diagnostic approaches for different types of cancer and other diseases. To enable such applications, the detection metrics of the devices must be optimized, including their sensitivity, selectivity, and stability. In particular, the capacitance of the device is one of the key determinants of the sensitivity of the electrical current of graphene to nearby changes in electrical potentials. In this presentation, we present our approach to optimize the surface capacitance of electrolyte-gated GFETs, by investigating theoretically and/or experimentally the effect of specific design parameters, including the graphene area, the removal of the backgate, and the passivation of electrodes. On the theoretical side, a mathematical representation of the device capacitance was established as an equivalent circuit of capacitors modelling for the quantum capacitance of graphene, the backgate capacitance, and the capacitance of electrical double layers in the electrolyte. On the experimental side, microchips of GFET arrays were assembled using microfabrication techniques on two types of substrates: a standard Si++/SiO2 wafer in which the doped silicon layer is used as a backgate, and a pure non-conducting borosilicate glass wafer in comparison. The capacitance of the devices was then measured using a custom parallel electrical prober by stepping the applied voltage in the solution and analyzing the resulting current response through a standard RC direct current model. We will present our analyses by comparing the relative impact of electrode passivation, backgate usage, and graphene area on the capacitance of devices. These results will enable a rational design of GFET devices with improved sensitivity for their use in applications such as biological, chemical, and gas sensing.

A chemosensitive-based ammonia gas sensor with PANI/PEO–ZnO nanofiber composites sensing layer

Purpose This study aims to investigate the ammonia-sensing performance of polyaniline/polyethylene oxide (PANI/PEO) and polyaniline/polyethylene oxide/zinc oxide (PANI/PEO-ZnO) composite nanofibers at room temperature. Design/methodology/approach Gas sensor structures were fabricated using microfabrication techniques. First, onto the SiO2 wafer, gold electrodes were fabricated via thermal evaporation. PANI/PEO nanofibers were produced by the electrospinning method, and the ZnO layer was deposited by using radio frequency (RF) magnetron sputtering on the electrospun nanofibers as a sensing layer. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction were performed to characterize the analysis of nanofibers. After all, gas sensing analysis of PANI/PEO and PANI/PEO/ZnO nanofibers was conducted using an experimental setup at room temperature conditions. Furthermore, the impact of humidity (17%–90% RH) on the sensor resistance was actively investigated. Findings FTIR analysis confirms the presence of functional groups of PANI, PEO and ZnO in nanofiber structure. SEM micrographs demonstrate beads-free, thinner and smooth nanofibers with ZnO contribution to electrospun PANI/PEO nanofibers. Moreover, according to the gas sensing results, the PANI/PEO nanofibers exhibit 115 s and 457 s response time and recovery time, respectively. However, the PANI/PEO/ZnO nanofibers exhibit 245 s and 153 s response time and recovery time, respectively. PANI/PEO/MOx composite nanofibers ensure stability to the NH3 gas owing to the high surface/volume ratio and decrease in the humidity dependence of gas sensors, making gas sensors more stable to the environment. Originality/value In this study, ZnO was deposited via RF magnetron sputtering techniques on PANI/PEO nanofibers as a different approach instead of in situ polymerization to investigate and enhance the sensor response and recovery time of the PANI/PEO/ZnO and PANI/PEO composite nanofibers to ammonia. These results indicated that ZnO can enhance the sensing properties of conductive polymer-based resistive sensors.

Surface Morphology and Exchange Bias Anisotropy Studies in Large Area Deposited Co2FeSi Ir50Mn50 Multi Layers For Spintronic Applications

Surface morphology and magnetic properties of ferromagnetic Heusler alloy Co2FeSi thin films and their multi-layers with anti-ferromagnetic Ir50Mn50, which find applications in spintronic devices were investigated. The sputtering process flow for large area deposition of thin films on 3 inch size thermally oxidized single crystal Si(100)/SiO2 substrates have been developed by optimizing the sputtering geometry and other process parameters. A uniform film composition, thickness, smooth surface, good crystallinity and magnetic properties have been achieved in the films over 3-inch size wafers. The isotropic magnetic properties such as saturation/remanent magnetizations, coercivity were achieved in Co2FeSi films deposited on 3-inch size Si(100)/SiO2 wafers with 15 nm Cr buffer layer. An exchange bias anisotropy has been established in Co2FeSi/IrMn multilayer by magnetic annealing process using in-house made magnetic annealing set up. A maximum exchange bias anisotropy field, Hex of 178 Oe and low coercivity, Hc of 85 Oe has been achieved in the Co2FeSi/IrMn multilayer stacks suitable for magnetic tunnel junctions for spintronic applications.

A chemosensitive based ammonia gas sensor with PANI/PEO- ZnO nanofiber composites sensing layer

Purpose The purpose of this study is to investigate the ammonia sensing performance of polyaniline/polyethylene oxide (PANI/PEO) and polyaniline/polyethylene oxide/zinc oxide (PANI/PEO-ZnO) composite nanofibers at room temperature. Design/methodology/approach Gas sensor structures were fabricated using micro-fabrication techniques. First, onto the SiO2 wafer, gold electrodes were fabricated via thermal evaporation. PANI/PEO nanofibers were produced by the electrospinning method and the ZnO layer was deposited by RF magnetron sputtering on the electrospun nanofibers as a sensing layer. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were performed for characterization analysis of nanofibers. After all, gas sensing analysis of PANI/PEO and PANI/PEO/ZnO nanofibers was performed using an experimental setup at room temperature conditions. Findings FTIR analysis confirms the presence of functional groups of PANI, PEO and ZnO in nanofiber structure. SEM images demonstrate beads-free, thinner and smooth nanofibers with ZnO contribution to electrospun PANI/PEO nanofibers. Moreover, according to the gas sensing results, the PANI/PEO nanofibers exhibit 115 and 457 s response time and recovery time, respectively. However, the PANI/PEO/ZnO nanofibers exhibit 245 and 153 s response time and recovery time, respectively. Originality/value In this study, ZnO was deposited via RF magnetron sputtering techniques on PANI/PEO nanofibers as a different approach instead of in situ polymerization, to investigate and enhance the sensor response and recovery time of the PANI/PEO/ZnO and PANI/PEO composite nanofibers to ammonia. These results indicated that ZnO can enhance the sensing properties of conductive polymer based resistive sensors.

Improvement of oxide chemical mechanical polishing performance by increasing Ce3+/Ce4+ ratio in ceria slurry via hydrogen reduction

Ceria-based abrasive is widely used in the oxide chemical mechanical polishing (CMP) process due to its high polishing performance. Ce3+ ions on the surface of ceria form a Ce–O–Si chemical bond with surface of the SiO2 wafer, significantly affecting the material removal rate (MRR). In this study, the ceria surface was reduced by contact with hydrogen gas in a high temperature isothermal environment. Hydrogen gas forms surface hydroxyls on the ceria. Then, the generated hydroxyls form H2O and oxygen vacancies occur through the desorption of the H2O. The color of ceria changed to blue due to a change of the crystal structure by the reduction reaction. The reducing ability of hydrogen gas increased as the reduction temperature increased and the Ce3+ ion concentration increased by 12.7% under isothermal conditions at 1000 °C. The MRR of reduced ceria was improved by up to 37.7% compared to the original ceria.

Assessment of AF4 Parylene Cohesion/Adhesion on Si and SiO2 Substrates by Means of Pull-Off Energy

Advanced packaging solutions require insulation and passivation materials with exceptional properties which can also fulfill the reliability needs of electronics devices such as MEMS, sensors or power modules. Since bonding (cohesive/adhesive) properties of packaging coatings are very important for reliable functioning of electronics devices, the bonding of aliphatic fluorinate-4 (AF4) parylene coatings was assessed in this work. As there is a lack of data regarding its bonding towards different substrates, pull-off tests of 1.6 and 2.5 μm thick AF4 coatings on silicon (Si) and glass (SiO2) substrates were performed. These showed a clear difference in the pull-off F/s curves between the AF4 coatings on Si and SiO2 substrates. This difference is parameterized by the pull-off energy, which will be presented in this work. To further understand the origin of the distinction in the pull-off energies between the AF4-Si and AF4-SiO2 samples and subsequently the cohesive/adhesive properties, mechanical and structural characterization was conducted on the AF4 coatings, where a clear difference in the E-modulus and crystallinity was observed. The Si and SiO2 wafers were shown to facilitate the CVD growth of the AF4 film distinctively, which likely relates to the divergent thermal properties of the substrates. Understanding of the cohesive/adhesive properties of AF4 coatings on different substrate materials advances the usage of the AF4 in electronics packaging technologies.

Effects of inorganic cations on the steric force between polyacrylamide layer physically adsorbed on SiO2 wafer and poly (ethylene oxide) layer

The physical adsorption of polyacrylamide on the SiO2 wafer in high salty solutions was investigated by an improved AFM steric force measurement. The colloid probe was modified by poly (ethylene oxide) layer and used to determine the steric force between adsorbed polyacrylamide and poly (ethylene oxide) layer in NaCl, KCl, MgCl2 and CaCl2 solutions. Assuming the adsorbed polyacrylamide complies with the self-similar model, the surface excesses, the thicknesses of the proximal regions, and "free energies of sticking" were estimated. Take the case of 5000 mg/L NaCl for example. The concentration profile was deduced from the corresponding steric force profile. The polyacrylamide concentration next to the SiO2 wafer was estimated to be about 147 g/L and the average concentration in the proximal region was estimated to be about 100 g/L. Based on the above estimations, interaction strength between the adsorbed cations and polyacrylamide was established, Mg2+ > Ca2+ > K+ > Na+. Moreover, the conformations of the adsorbed polyacrylamide were changed from "lying flat" to folded ones by the stronger interactions between the adsorbed cations and polyacrylamide.”

Interfacial properties of 2D WS2 on SiO2 substrate from X-ray photoelectron spectroscopy and first-principles calculations

Two-dimensional (2D) WS2 films were deposited on SiO2 wafers, and the related interfacial properties were investigated by high-resolution X-ray photoelectron spectroscopy (XPS) and first-principles calculations. Using the direct (indirect) method, the valence band offset (VBO) at monolayer WS2/SiO2 interface was found to be 3.97 eV (3.86 eV), and the conduction band offset (CBO) was 2.70 eV (2.81 eV). Furthermore, the VBO (CBO) at bulk WS2/SiO2 interface is found to be about 0.48 eV (0.33 eV) larger due to the inter-layer orbital coupling and splitting of valence and conduction band edges. Therefore, the WS2/SiO2 heterostructure has a Type I energy-band alignment. The band offsets obtained experimentally and theoretically are consistent except the narrower theoretical bandgap of SiO2. The theoretical calculations further reveal a binding energy of 75 meV per S atom and the totally separated partial density of states, indicating a weak interaction and negligible Fermi level pinning effect between WS2 monolayer and SiO2 surface. Our combined experimental and theoretical results provide proof of the sufficient VBOs and CBOs and weak interaction in 2D WS2/SiO2 heterostructures.

Characterization of Microtransformers with Magnetic Ni-Fe-W alloy Cores Plated at Two Different Substrate Temperatures

The electroplating technique is used to realize microtransformers on a SiO2 wafer. The magnetic core of these microtransformers is deposited at a substrate temperature of 5 °C and 21 °C, while the core material is the same. For the fabrication of the magnetic core (3 µm thick), Ni-Fe-W alloy film is utilized. These fabricated transformers show changes in performance due to variations in core properties. The transformers whose core is fabricated at substrate temperature 21 °C have a significantly higher inductance than the microtransformers whose core is fabricated at a substrate temperature of 5 °C. However, the core fabricated at 5 °C has better magnetic properties than the core fabricated at 21 °C. An impedance analyzer is employed for the characterization of transformers. A signal of 5 mA at 1 MHz is used to obtain the inductance of transformers. The maximum inductance of transformers in which cores are fabricated at 5 °C and 21 °C are 54 nH and 68 nH and almost continuous up to 30 MHz, respectively. A maximum quality factor of 3.51 is attained at 15 MHz.

Quartz Tuning Fork Sensor-Based Dosimetry for Sensitive Detection of Gamma Radiation.

This study generally relates to nuclear sensors and specifically to detecting nuclear and electromagnetic radiation using an ultrasensitive quartz tuning fork (QTF) sensor. We aim to detect low doses of gamma radiation with fast response time using QTF. Three different types of QTFs (uncoated and gold coated) were used in this study in order to investigate their sensitivity to gamma radiations. Our results show that a thick gold coating on QTF can enhance the quality factor and increase the resonance frequency from 32.7 to 32.9 kHz as compared to uncoated QTF. The results also show that increasing the surface area of the gold coating on the QTF can significantly enhance the sensitivity of the QTF to radiation. We investigated the properties of gold-coated and uncoated QTFs before and after irradiation by scanning electron microscopy. We further investigated the optical properties of SiO2 wafers (quartz) by spectroscopic ellipsometry (SE). The SE studies revealed that even a small change in the microstructure of the material caused by gamma radiation would have an impact on mechanical properties of QTF, resulting in a shift in resonance frequency. Overall, the results of the experiments demonstrated the feasibility of using QTF sensors as an easy to use, low-cost, and sensitive radiation detector.

Short-Pulse Laser-Assisted Fabrication of a Si-SiO2 Microcooling Device.

Thermal management is one of the main challenges in the most demanding detector technologies and for the future of microelectronics. Microfluidic cooling has been proposed as a fully integrated solution to the heat dissipation problem in modern high-power microelectronics. Traditional manufacturing of silicon-based microfluidic devices involves advanced, mask-based lithography techniques for surface patterning. The limited availability of such facilities prevents widespread development and use. We demonstrate the relevance of maskless laser writing to advantageously replace lithographic steps and provide a more prototype-friendly process flow. We use a 20 W infrared laser with a pulse duration of 50 ps to engrave and drill a 525 μm-thick silicon wafer. Anodic bonding to a SiO2 wafer is used to encapsulate the patterned surface. Mechanically clamped inlet/outlet connectors complete the fully operational microcooling device. The functionality of the device has been validated by thermofluidic measurements. Our approach constitutes a modular microfabrication solution that should facilitate prototyping studies of new concepts for co-designed electronics and microfluidics.

Femtojoule‐Power‐Consuming Synaptic Memtransistor Based on Mott Transition of Multiphasic Vanadium Oxides

AbstractTo realize the potential of Mott transition of multiphasic vanadium oxides (VOx) for memory applications, the development of VOx memtransistors on SiO2 wafer is introduced. Through electrical characterizations, the volatile memory behaviors of the VOx memtransistors are observed in both two‐ and three‐terminal measurements. Their capacitive memory and resistive switching mechanisms are strongly related to the mixed VOx/SiO2 interface (called VSiOx). VSiOx supports the Mott transition in VOx at low bias voltages (<0.5 V), leading to the low power consumption of the memtransistor. Moreover, the fast switching time (≈35 ns) and tunable memory retention with the synaptic functions (potentiation and depression) of the memtransistors (by using the gate and drain biases) are demonstrated. Overall, the findings open up major opportunities for constructing ultrafast and femto‐joule power‐consuming neuromorphic devices.

Enhancing the Conductivity of the Nanostructured ZnO Thin Film by Vacuum Annealing

ZnO thin films were successfully synthesized using a facile chemical route and were characterized employing X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and photoluminescence (PL) analysis. The obtained precursor was spin-coated on Si(100)/SiO2 wafers, then the substrates were divided into two groups for the thermal annealing at ambient and vacuum conditions. Morphological characterization showed the formation of nanoflowers and porous structures at different annealing conditions. The effect of vacuum annealing on the current-voltage characterization of ZnO thin film has been presented to inspect the role of annealing condition in device fabrication. The electrical properties of the ZnO thin films were performed in the temperature range of 75–[Formula: see text]C. At [Formula: see text]C, the ambient annealed sample presents the current value of 10[Formula: see text][Formula: see text]A for 5[Formula: see text]V, and the vacuum annealed sample reaches the maximum current of 3.1[Formula: see text]mA for the same operating voltage. The presence of oxygen vacancies notably affects the electrical properties of ZnO thin films.

Plasma-induced oxygen vacancies enabled ultrathin ZnO films for highly sensitive detection of triethylamine

Metal oxide semiconductor (MOS) thin films hold great promise for electronic devices such as gas sensors. However, the low surface activity of pristine MOS often leads to inferior sensitivity and the sensitization mechanism of ultrathin MOS films has received rare attention. Herein, we report a high performance gas sensor based on plasma-etched ZnO thin films. The ultrathin ZnO films (20 nm) were deposited on SiO2 wafers by atomic layer deposition (ALD), which enables high-throughput production of sensor devices. The ZnO sensor shows typical n-type conductivity, which is highly variable to the exposure of triethylamine (TEA). Annealing temperature of the films is found to impact the sensor response, revealing calcination at a moderate temperature, i.e. 700 °C, leads to the best response. Further treatment by Ar plasma results in a remarkable decrease of sensor working temperature from 300 °C of untreated films to 250 °C and nearly 4-fold enhancement in the sensor response to 10 ppm TEA. Notably, the plasma-treated ZnO sensor also shows decent response even at room temperature (RT), which has been seldom reported for ZnO-based sensors. Structure and mechanism investigations reveal that the superior sensor properties are derived from the abundant oxygen vacancies generated by Ar plasma etching.