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This Letter aims to promote basic research into memristors, which will help provide theorists with much-needed reliable benchmarks and will also aid the technology progress. It addresses an information gap presently in the literature on simple microfabrication techniques for the realisation of such devices. Consequently, a fabrication method is reported for implementing the full active-material stack, requiring a single lithography and evaporation step. A cost-effective technique that can reliably shrink device lateral dimensions towards the nanoscale is also demonstrated. Experimental results confirm the suitability of the proposed methods for fabricating memristors of varying dimensions that exhibit consistent electrical characteristics. [ABSTRACT FROM AUTHOR]

Bulk-drain connected PMOS transistors are proposed as loads for subthreshold MOS current-mode logic gates. Such loads exhibit an approximately linear dependence of the subthreshold drain-source current on the drain-source voltage, guaranteeing robust gate operation. The design and performance of an inverter gate and ring oscillator in a 0.25 µm CMOS technology are presented. [ABSTRACT FROM AUTHOR]

A fundamental relationship exists between diffusion characteristics within semiconductors and Nernstian equilibrium in biological systems. In a transistor operating in weak inversion the potential difference between terminals governs electron concentration in an exponential way according to the Boltzmann distribution of charged particles while in a biochemical cell the potential difference across a membrane is governed by ionic concentration in a logarithmic way according to the Nernst equation. These two nonlinear physical phenomena form an interaction that potentially leads to linearisation and subsequent modelling of or interaction with biological systems by integrated semiconductor devices. To demonstrate the authors' hypothesis a silicon transistor-based biosensor is considered. This natural bridge between biochemistry and semiconductor silicon chips will enable the potential mass production of portable biochemical devices for the consumer market. [ABSTRACT FROM AUTHOR]

Proposed is an ISFET readout scheme with minimum analogue components to minimise parasitic and noise effects in large-scale chemical sensing arrays. For each array pixel, a pair of complementary ISFETs shares the same floating gate in an inverter configuration. An additional electrical input is capacitively coupled to the same floating gate with a periodic reference signal input. In this way, the conventional ISFET analogue output is replaced by a chemically controlled pulse width modulated signal. Theoretical analysis and experimental results show a pulse width pH sensitivity of around 6%, of the input reference signal period, per pH. This is achieved along with ±1 V offset suppressing capability. [ABSTRACT FROM AUTHOR]

Ion sensitive field effect transistors (ISFETs) fabricated in standard CMOS process are effectively floating gate devices. These ISFETs generally suffer from large threshold voltage variations owing to trapped charges. Aiming to reduce mismatch in ISFET arrays, it is shown in this reported work that Fowler-Nordheim electron tunnelling can be used to program charges in the floating gate of an ISFET in order to control its threshold voltage. The threshold voltage of a p-ISFET fabricated in 0.35 µm CMOS process was shifted by -3.45 V in a pH 7.0 buffer solution. [ABSTRACT FROM AUTHOR]

The use of hot-electron injection as a method for programming the threshold voltages of CMOS based ion-sensitive field-effect transistors (ISFETs) in standard pH buffer solution is presented. This method allows compensation of large threshold voltage variations generally seen with ISFETs fabricated in unmodified CMOS due to the presence of trapped charge, enabling operation of the device using nominal supply voltage as well as reduction of mismatch between devices when fabricating ISFET arrays. Fabricated in a 0.35 µm CMOS process, threshold voltage shifts of up to 2.8 V have been achieved in a pH 7 buffer solution. [ABSTRACT FROM AUTHOR]