Optimization of a Boron Doped Nanocrystalline Diamond Temperature Regulator for Sensing Applications
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Optimization of a Boron Doped Nanocrystalline Diamond Temperature Regulator for Sensing Applications Tim Clukers1,2, Bart Van Grinsven1, Thijs Vandenryt1,2, Stoffel D. Janssens1, Patrick Wagner1,3, Ward De Ceuninck1,3, Ronald Thoelen1,2, Michaël Daenen1,2 and Ken Haenen 1,3 1 Hasselt University, Institute for Materials Research (IMO), Wetenschapspark 1, 3590 Diepenbeek, Belgium 2 Xios University College Limburg, Agoralaan H, 3590 Diepenbeek, Belgium 3 IMEC vzw, Division IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, Belgium ABSTRACT Recently, the concept of creating a boron doped nanocrystalline diamond (B-NCD) based temperature regulator for bio-sensing applications was proven. In this work, the next step is taken, i.e. one device working simultaneously as thermistor and heater. In combination with a PID-control., it is possible to create a temperature control, with possible set points going from room temperature till 70°C, with an accuracy exceeding a maximum temperature variation of 0.2 °C. Parallel with steering the temperature by varying the current through the B-NCD film, its resistance is measured with a 4-point measurement from which the temperature can be derived using a calibration curve. This value is the feedback for the PID-control to steer the current used for the regulation. INTRODUCTION When monitoring biological samples, it is known that the conditions of the immediate surroundings of the measurement setup are of great importance and can have a major influence on the outcome, especially when such samples are highly temperature dependent. A solution in this respect is to control the environment as accurately as possible, hence the necessary temperature regulation. As diamond provides a stable biological platform and can be made semiconducting by doping it with boron (B-NCD), enabling to use it as a temperature sensor and regulator, it is an ideal material to be steer the surrounding temperature by letting the B-NCD film act as a resistor [1-4]. The conductivity of B-NCD layers can be easily controlled by a variation of the dopant content during the deposition process [5], and when using a semiconducting B-NCD sample it is known that with decreasing the temperature, the amount of charge carriers will decrease accordingly. Based on this principle, it must be possible to link the temperature of the immediate surroundings directly linked to the resistivity of the thin diamond layer [6]. In addition, the B-NCD layer can also act as a resistor, facilitating heating of its immediate surroundings using the Joule effect. So it is possible to create a device that can sense and steer the temperature of the environment at the same time. Before these facts can be used in an automated steering device, it is indispensable to find an explicit mathematical relation between temperature and resistivity. By measuring the resistance of the sample in function of temperature the required calibration curves can be determined.
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EXPERIMENT The 150 nm thick B-NCD growth onto a standard quartz sample of 1 x 1 cm² was carried
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