Abstract
This paper presents a thin film structure suitable for low-level radiation measurements in lab-on-chip systems that are subject to thermal treatments of the analyte and/or to large temperature variations. The device is the series connection of two amorphous silicon/amorphous silicon carbide heterojunctions designed to perform differential current measurements. The two diodes experience the same temperature, while only one is exposed to the incident radiation. Under these conditions, temperature and light are the common and differential mode signals, respectively. A proper electrical connection reads the differential current of the two diodes (ideally the photocurrent) as the output signal. The experimental characterization shows the benefits of the differential structure in minimizing the temperature effects with respect to a single diode operation. In particular, when the temperature varies from 23 to 50 °C, the proposed device shows a common mode rejection ratio up to 24 dB and reduces of a factor of three the error in detecting very low-intensity light signals.
Highlights
Lab-on-Chip (LoC) systems have seen remarkable development in the fields of biology and chemistry, because they can perform biochemical analyses with smaller volumes of reagent and in shorter times than standard methods [1]
On-chip detection methods, based on thin film organic and inorganic sensors have been proposed [3,4,5] as substitutes of cooled charge coupled devices or complementary-metal-oxide-semiconductor imagers, to allow the fabrication of more compact LoC
The basic structure of the photosensors is an amorphous silicon carbide (a-SiC:H) p-doped/intrinsic a-Si:H/n-doped a-Si:H stack deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD)
Summary
Lab-on-Chip (LoC) systems have seen remarkable development in the fields of biology and chemistry, because they can perform biochemical analyses with smaller volumes of reagent and in shorter times than standard methods [1]. The glass substrate hosting the photosensors can be used as an for a microfluidic other materials, polymers, are fabricated active mechanical network support made for a from microfluidic networkincluding made from other which materials, including polymers, which are fabricated lowerphotosensors temperatures.present. In the proposed properly connected to measure the difference proposed structure, one diode is light-shielded and its current depends only on temperature, while the current of the other diode depends on temperature and light Under these conditions, the current induced by temperature is the common signal, while photocurrent photocurrent is is the the differential differential signal. 4 experimentally describes the efficacy of device in rejecting the temperature common mode signals, Section presents the conclusions.
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