Development of Si Nanowire Chemical Sensors (original) (raw)
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Sensor system including silicon nanowire ion sensitive FET arrays and CMOS readout
Sensors and Actuators B: Chemical, 2014
We present a highly sensitive chemical sensor system including a chip with an array of silicon nanowire ISFETs and a CMOS chip with custom-designed signal-conditioning circuitry. The CMOS circuitry, comprising 8 sigma-delta ( -) modulators and 8 current-to-frequency converters, has been interfaced to each of the nanowires to apply a constant voltage for measuring the respective current through the nanowire. Each nanowire has a dedicated readout channel, so that no multiplexing is required, which helps to avoid leakage current issues. The analog signal has been digitized on chip and transmitted to a host PC via a FPGA. The system has been successfully fabricated and tested and features, depending on the settings, noise values as low as 8.2 pA RMS and a resolution of 13.3 bits while covering an input current range from 200 pA to 3 A. The two readout architectures ( -and current to frequency) have been compared, and measurements showing the advantages of combining a CMOS readout with silicon nanowire sensors are presented: (1) simultaneous readout of different silicon nanowires for high-temporal-resolution experiments and parallel sensor experiments (results from pH and KCl concentration sweeps are presented); (2) high speed measurements showing how the CMOS chip can enhance the performance of the nanowire sensors by compensating its non-idealities as a consequence of hysteresis.
2015
We present a monolithic CMOS-based sensor system comprising an array of silicon nanowire field-effect transistors (FETs) and the signal-conditioning circuitry on the same chip. The silicon nanowires were fabricated by chemical vapor deposition methods and then transferred to the CMOS chip, where Ti/Pd/Ti contacts had been patterned via e-beam lithography. The on-chip circuitry measures the current flowing through each nanowire FET upon applying a constant source-drain voltage. The analog signal is digitized on chip and then transmitted to a receiving unit. The system has been successfully fabricated and tested by acquiring I-V curves of the bare nanowire-based FETs. Furthermore, the sensing capabilities of the complete system have been demonstrated by recording current changes upon nanowire exposure to solutions of different pHs, as well as by detecting different concentrations of Troponin T biomarkers (cTnT) through antibody-functionalized nanowire FETs.
Top-down Fabrication of Si Nanowire and Fully Automated Test Platform: Application to pH Sensor
2000
Detection and quantification of very small amounts of biological species become necessary to allow an early detection of malignant disease and the development of personalized medicine. Currently, fluorescence detection or colorimetry are the most frequently used techniques. Although very sensitive, the necessary labelling step of the biotargets can alter their recognition properties and these methods have a low potential for
A pH sensor with a double-gate silicon nanowire field-effect transistor
Applied Physics Letters, 2013
A pH sensor composed of a double-gate silicon nanowire field-effect transistor (DG Si-NW FET) is demonstrated. The proposed DG Si-NW FET allows the independent addressing of the gate voltage and hence improves the sensing capability through an application of asymmetric gate voltage between the two gates. One gate is a driving gate which controls the current flow, and the other is a supporting gate which amplifies the shift of the threshold voltage, which is a sensing metric, and which arises from changes in the pH. The pH signal is also amplified through modulation of the gate oxide thickness. V
Design, realization and characterization of silicon nanowire ion sensitive field effect transistors
2016 IEEE Nanotechnology Materials and Devices Conference (NMDC), 2016
The aim of our research project is to achieve a potentiometric multi-sensor platform, consisting of ion sensitive field effect transistors ISFET and MOSFET, which channel is a nanowire or a network of horizontal Silicon nanowires and whose gate insulator is alumina Al2O3 deposed by Atomic Layer deposition ALD. This microdevice will provide chemical and biological analyses in the liquid phase, in microfluidic channels.
2011
We have fabricated Si nanowire (SiNW) based ion-sensitive field effect transistors (ISFETs) for biosensing applications. The ability to prepare a large number of sensors on a wafer, the use of standard silicon microfabrication techniques resulting in cost savings, and potential high sensitivity are significant advantages in favor of nanoscale SiNW ISFETs. The SiNW ISFETs with embedded Ag/ AgCl reference electrode were fabricated on a standard silicon-on-insulator wafer using electron-beam lithography and conventional semiconductor processing technology. The current-voltage characteristics show an n-type FET behavior with a relatively high on/off current ratio, reasonable subthreshold swing value, and low gate-leakage current. The pH responses of the ISFETs with different pH solutions were characterized at room temperature which showed a clear lateral shift of the drain current vs. gate voltage curve with a change in the pH value of the solution and a sensitivity of 40 mV pH À1 . The low frequency noise characteristics were investigated to evaluate the signal to noise ratio and sensing limit of the devices.
Silicon nanowires synthesis for chemical sensor applications
Procedia Engineering, 2010
Silicon nanowires (SiNWs) are synthesized following two methods: i) the VLS (Vapor-Liquid-Solid) growth technique (bottom up approach), and ii) the sidewall spacer fabrication (top down approach) commonly used in microelectronic industry. The VLS growth technique uses gold nanoparticles to activate the vapor deposition of the precursor gas and initiate a 100 nm diameter SiNWs network growth. In the case of the sidewall spacer method, a polysilicon layer is deposited by LPCVD (Low Pressure Chemical Vapor Deposition) technique on SiO 2 wall patterned by conventional UV lithography technique. Polysilicon film is then plasma etched. Accurate control of the etching rate leads to the formation of spacers with a 100 nm curvature radius that can be used as polysilicon NWs. Each kind of nanowires is integrated into resistors fabrication. Electrical measurements show the potential usefulness of these SiNWs as chemical sensors.
Amino-propyltriethoxysilane Modified Heavy Metal Sensor Based on Silicon Nanowire Arrays
IOP Conference Series: Materials Science and Engineering
Safety of consuming water from various resources can be questioned nowadays due to high content of material that is highly possible to have toxic content and cause permanent damage to human itself. Possible toxic content includes heavy metal such as lead, arsenic, cadmium and mercury. A highly sensitive or selective heavy metal sensor needed to aid in detection of these metal species. In this paper, the manipulation of silicon nanowire to detect heavy metal content in liquid sample is explained. Device is fabricated into two main elements which is the detecting part which is the nanowire and probes on the both sides. Next, the characterizations of the device are discussed as well as the discussion on the detections capabilities. The APTES surface modified integrated electrochemical nano-sensor was subjected to various concentration of lead ions, the responses were monitored assessed for the detection ion chemical activities, this response were observed using semiconductor parametric analyzer (SPA). The surface modified nano-sensor show a linear behavior with current response between 2-140pA, the detection limit for the lead ions was 0.1µm/l. The water samples which were collected in Taman Tasik Damam in Malaysia show similar characterization for area of around 20 square meters. Thus, the excellent and reliable behavior shown by this device, it can be adopted as detection device for various heavy metal detection in near future.