Wafer-scale fabrication of conformal atomic-layered TiO2 by atomic layer deposition using tetrakis (dimethylamino) titanium and H2O precursors

Interdigitated electrode (IDE) based electrical biosensors are promising in the medical application field. The aim of the research study is design, fabricate and characterize of low cost, high sensitive biosensor for medical applications. IDE pattern was designed using AutoCAD software with 1 μm finger gap. Fabrication process was done using conventional photolithography process and standard CMOS process. Fabricated electrode was physically characterized using SEM images, electrically validated through I–V measurements and chemically tested with different pH buffer solutions. Al IDE was well fabricated with 0.1 μm tolerance between design mask and fabricated IDEs. Electrical measurements confirmed that IDE was well fabricated without any shortage and results of similar IDE samples were confirmed that the repeatability of the device. The extremely small current variations in nano ampere range were quantitatively detected using extra small volume of 1 μl for different pH buffer solutions. It is confirmed that IDEs are sensitive in both alkali and hydroxyl ions medium.

Design, fabrication and characterization of 1.0 μm Gap Al based interdigitated electrode for biosensors

High sensitivity and reliability of graphene oxide (GO) integrated with aluminum (Al) micro-interdigitated electrodes ( $\mu $ -IDEs) patterned on p-Si for the detection of aqueous fluoride anion (F−) is demonstrated. The strong molecular interaction, hydrogen bonding, and ionic conduction between the oxygen containing functional groups (epoxy (1, 2-ether), hydroxyl, carbonyl, and carboxyl) onto GO and F− are investigated by electrical and optical techniques. The GO/Al ( $\mu $ -IDEs)/p-Si sensor system shows $\sim 82$ % increase in the sensing signal for 0.1 ppm GO + F− solution with respect to GO. The response of the sensor for 1, 10, 100, and 1000 ppm of GO + F− solution shows almost 220, 415, 500, and 305 times increase in sensing signal with respect to GO. The significant enhancement in sensor response at lower concentration (0.1–100 ppm) of F− is observed. However, at high concentration (1000 ppm) of F−, the interlayer swelling and the expansion of GO dominate and result the reduction in sensing response of GO/Al ( $\mu $ -IDEs)/p-Si sensor. The Fourier transform infrared spectroscopy (FT-IR) spectra show the decrease in –OH, C–O–C, and CLO absorption peaks of GO with an increasing aqueous F− concentration, supporting the reduction in sensing response at 1000 ppm. The response of GO/Al ( $\mu $ -IDEs)/p-Si sensor is favorable for use in graphene-based electronics sensors.

Integration of Highly Sensitive Oxygenated Graphene With Aluminum Micro-Interdigitated Electrode Array Based Molecular Sensor for Detection of Aqueous Fluoride Anions

Ti-doped ZnO nanorods (NRs) have been deposited onto Si substrates at 93 °C by using chemical bath deposition method. FESEM observations show high-quality NRs. FTIR spectra display main peak around 560 cm−1 associated with Zn–O bond in addition to minor peak detected around 500 cm−1 referred to Ti–O bond. XRD patterns reveal the presence of the main (002) peak of the hexagonal wurtzite structure for all prepared films, where its intensity increases with increasing Ti doping, thereby indicating a very strong preferred orientation and batter crystallinity. Photoluminescence spectra exhibit a strong enhancement in both UV and visible emissions after Ti doping. Similarly, Raman spectroscopy shows sharp increment in E2(H) mode in doped films. The enhancement mechanism in both structural and optical properties of Ti-doped ZnO films have been investigated.

Structural and optical characteristics of Ti-doped ZnO nanorods deposited by simple chemical bath deposition

There is considerable interest in nanostructured materials with interdigitated electrodes (IDEs) platforms to detect and monitor the level of various ions in numerous applications. Herein, we report the design and fabrication of IDEs based pH sensor by using hydrothermal growth of ZnO nanorods (NRs). A four-step deposition of ZnO seed layer followed by a hydrothermal treatment lead to the heavily ordered ZnO NRs patterns on the screen printed IDEs. The structural, chemical compositional and electrical properties of the NRs were investigated and examined by using field emission scanning electron microscopy (FeSEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) technique and Keithley 4200 semiconductor characterization system respectively. The sensor capacitance and pH were found to be inversely proportional at a working frequency of 1 kHz. The sensor displayed sensitivity of 1.06 nF/pH in the range of pH 4−10.

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Hydrothermal Growth of Zinc Oxide (ZnO) Nanorods (NRs) on Screen Printed IDEs for pH Measurement Application

Fabrication and characterization of titanium dioxide (TiO2) thin film on Al/TiO2/SiO2/p-Si MIS structure for the study of morphology, optical and electrical properties were reported. A transparent and high crystallinity of TiO2 thin films were prepared at room temperature (~25 °C) by sol---gel route. TiO2 sol suspension were prepared at molar ratio of TTIP:EtOH:AA = 2:15:1 using titanium tetra-isopropoxide (TTIP) and a mixture of absolute ethanol (EtOH) and acetic acid (AA) which used as a precursor and catalyst for the peptization, respectively. The TiO2 thin films were deposited on a thermally grown SiO2 layer of p-type silicon (100) substrates and were thermally treated at different annealing temperatures of 300, 500, 700 and 900 °C. For study of optical properties, the TiO2 thin films were deposited on a glass slides substrate and were annealed from 200 to 700 °C. The XRD results show that the presence of an amorphous TiO2 phases were transformed into the polycrystalline (anatase or rutile) with good crystallinity after treated at higher annealing temperatures. Besides, the surface roughness of TiO2 thin films increased with increasing annealing temperatures. In addition, the resistivity of the thin films decreased from 2.5751E+8 to 6.714E+7 ? cm with the increasing temperatures. Moreover, the optical absorbance of TiO2 thin films exhibited high UV---visible light absorption with band gap energy shifted to the higher wavelength (low energy photons). The band gap energy (Eg) of the films decreased from 3.79 to 3.16 eV and from 3.95 to 3.75 eV significantly for direct band allowed and indirect band allowed, respectively, with the increasing annealing temperatures.

Effect of annealing temperatures on the morphology, optical and electrical properties of TiO2 thin films synthesized by the sol---gel method and deposited on Al/TiO2/SiO2/p-Si

Micro interdigitated electrodes (IDE's) have successfully been fabricated and characterized amperometrically for the electrochemical detection of the pH concentration and bio-molecules. In the present work, aluminium (Al) is used act as the metal contact (electrodes) deposited on the silicon substrate using a thermal evaporator (PVD) vacuum coater. The simple conventional photolithography was applied to fabricate the micro-gap capacitive transducer. IDE's mask is designed using the aid of AutoCAD software for the detection of bio-substance which is an extremely small scale in size before being transferred to commercial chrome mask. The fabricated micro-gap sensor will then further evaluated through surface topology and electrical characteristic. The surface topology was implemented using AFM, LPM, SEM and HPM. The electrical measurements were carried out using a Dielectric analyzer (DA) with 2400 source meter (KEITHLEY) to examine the electrical characteristics such as capacitance and conductance. Purchased pH buffer solutions which varied from pH4 to pH 10 is dropped on the surface of microelectrode and the effect on it is investigated for the application in pH measurement. This study has proven that an increase in the concentration of acidic to alkaline pH leads to proportional to the capacitance.

Fabrication of interdigitated electrodes (IDE's) by conventional photolithography technique for pH measurement using micro-gap structure

Titanium dioxide (TiO2) thin films were successfully prepared using the use of titanium isopropoxide as a precursor with an ethyl alcohol solution at a molar ratio 1.0:10 by sol-gel precipitation method at room temperature (~24°C). The gel solution was formed after mixed for different times. TiO2 thin films were deposited on the P-type silicon substrates by spin coating technique. In this paper, we report the comparison between conductivity and resistivity of TiO2 thin films prepared at different heat treatment. The results show that the electrical properties of TiO2 thin film were changed with the changes of heat treatment. The results exhibit that the resistance tends to decline as the annealing temperature increases. The most conductive sample is 700°C followed with 500°C, 300°C, 100°C and least conductive is as-deposited film. From the I-V curve, the graph giving a Schottky contact properties.

Electrical Properties of Nano-TiO2 Thin Film Prepared by Sol-Gel Precipitation Route Using Two-Point Probe Method

Currently, the potential use of Semiconductor nanowires as parts of future devices has triggered an increased interest in biosensor research. The COMSOL Multiphysics is simulation used that can improve the sensitivity of Bioelectronics to extend their stability and utility. In this paper, we are investigating the effect of DNA concentration of the electrolyte effect biosensor on the conductance of the nanowire through finite element calculations. First, the distribution of the electrostatic has potential in the nanowire due to the DNA concentration. In conclusion of this paper represented DNA that conductance nanowire is affected from surface modification after DNA including on the model.

The Field Effect of Concentration DNA on Conductance of Silicon Nanowire

In the present research, nanocrystalline TiO2 thin films have been prepared via a sol-gel method using Ti {OCH(CH3)2}4 act as a precursor. The morphological effect of sets of as-deposited and annealed samples (100, 300, 500 and 700°C for 1 hour) and thickness variation on the structural properties were investigated by Atomic Force Microscopy (AFM) measurements. The observation showed that the size of grain increases with film thickness, indicating that the size of the particles in the films can be effectively controlled by changing the temperature of thermal treatment. AFM topology images of the as-deposited and annealed TiO2 films at 100 and 300°C indicates the films are rather smooth, compact, bulky, not uniform and column-like structure. TiO2 thin films annealed at 500 and 700°C showed homogenous morphology surface with regular size of spherical particles.

A.K.M. Muaz

Papers

Effect of annealing temperatures on the morphology, optical and electrical properties of TiO2 thin films synthesized by the sol---gel method and deposited on Al/TiO2/SiO2/p-Si

Fabrication of interdigitated electrodes (IDE's) by conventional photolithography technique for pH measurement using micro-gap structure

Electrical Properties of Nano-TiO2 Thin Film Prepared by Sol-Gel Precipitation Route Using Two-Point Probe Method

The Field Effect of Concentration DNA on Conductance of Silicon Nanowire

Preparation and Characterization of SiO2-Coated TiO2 Thin Films via Sol-Gel Dip Coating Technique