Joachim P. Kloock

Inorganic Thin-film Sensor Membranes with PLD-prepared Chalcogenide Glasses: Challenges and Implementation

Chalcogenide glasses offer an excellent “challenge” for their use and implementation in sensor arrays due to their good sensor-specific advantages in comparison to their crystalline counterparts. This paper will give an introduction on the preparation of chalcogenide glasses in the thin-film state. First, single microsensors have been prepared with the methods of semiconductor technology. In a next step, three microsensors are implemented onto one single silicon substrate to an “one chip” sensor array. Different ionselective chalcogenide glass membranes (PbSAgIAs2S3, CdSAgIAs2S3, CuAgAsSeTe and TlAgAsIS) were prepared by means of the pulsed laser deposition (PLD) process. The different sensor membranes and structures have been physically characterized by means of Rutherford backscattering spectrometry, scanning electron microscopy and video microscopy. The electrochemical behavior has been investigated by potentiometric measurements.

A Semiconductor-based Field-effect Platform for (Bio-)Chemical and Physical sensors: From Capacitive EIS Sensors and LAPS over ISFETs to Nano-scale Devices

The coupling of semiconductor field-effect devices (FED) together with chemical and biological recognition elements, like functional intelligent materials, biomolecules and living cells, represents an attractive platform for the creation of different (bio-)chemical sensors, multi-parameter analysis systems and bio-chips. This paper summarises recent developments and current research activities in the field of (bio-)chemically modified FEDs, scaling down from capacitive EIS (electrolyte-insulator-semiconductor) sensors and LAPS (light-addressable potentiometric sensor) to ISFETs (ion-sensitive field-effect transistor) that have been realised in our laboratory. Selected examples of application of ISFETs for the detection of physical parameters in liquids are presented, too. With the aim of future development of nano-devices for the detection of single biomolecules, the possibility of a simple preparation of different self-aligned nano-structures by using conventional photolithography and pattern-size reduction technique has been experimentally demonstrated.

Procedure 6 Determination of cadmium concentration and pH value in aqueous solutions by means of a handheld light-addressable potentiometric sensor (LAPS) device

Publisher Summary This chapter discusses the fabrication of a light-addressable potentiometric sensor (LAPS) for the detection of the pH value and the cadmium-ion concentration in aqueous solutions. For the pH-sensitive LAPS, use, e.g., Ta 2 O 5 as a sensor membrane, and for the cadmiumselective LAPS, use a Cd 2+ -selective chalcogenide glass thin film as a heavy metal-sensitive material. The electrochemical sensor characterization of the LAPS structure performs current vs. voltage (I/V) and constant current (CC) measurements. The presented protocol provides a basic idea of a typical LAPS set-up. The number of measurement spots and the size of the sensor chip can vary for different applications. The position of the light sources as well as the position of the amplifier stage is of great importance for the signal stability and should be as close as possible to the sensor chip. Furthermore, the conductivity of the electrolyte solution has to be taken into account for low conductive solutions. The initial I/V and CC measurements, as demonstrated in this protocol, are important to evaluate the system performance and provide a wide range of useful information.