A Highly Sensitive Temperature Sensor Based on Au/Graphene-PVP/<i>n</i>-Si Type Schottky Diodes and the Possible Conduction Mechanisms in the Wide Range Temperatures
Osman Çіçek, Ş. Altındal, Yashar Azizian‐Kalandaragh
Abstract
We report that the sensitive temperature response and possible Conduction Mechanisms (CMs) of Au/graphene-PVP/ n-Si type Schottky diodes (SDs) are investigated using the standard Thermionic Emission (TE) theory at low temperatures (LTs) and high temperatures (HTs). The obtained results indicate that the zero-apparent barrier height (φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bo</sub> -φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ap</sub> ) increases while the ideality factor (n), series and shunt resistances (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> , R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sh</sub> ), rectifying rate (at ±2V) and surface states (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> ) decrease with increasing temperature. The φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bo</sub> , n and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> values are also extracted from Cheung's functions and, then compared with those obtained TE theory. The conventional Richardson plot (ℓn(I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> /T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )-q/kT) displays the deviation from the linearity at low-temperatures (T ≤ 140 K). Besides, the experimental value of Richardson constant (A*) deduced from the intercept of plot was found to be several orders lower than the theoretical value. The discrepanciesand higher values for the parameter of n are important evidences for the deviation from TE theory. This is mainly attributed to the spatial inhomogeneities of the barrier height and potential fluctuations at the interface including low/high barrier areas. Hence the CMs across diode preferentially flows through these lower barriers/patches at the regions of LTs. The decrement in the N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> with the enhancement in the temperature is in relation to the molecular restructuring-reordering under temperature and voltage effects. The SDs fabricated with graphene-PVP interlayer exhibit a higher sensitivity (S) rather than many silicon/SOI-based structures. Numerically, the S values are found to be in a range of 1.3 mV/K (LTs)/-1.93mV/K (HTs) in case of I = 0.1 μA as against much greater values of -8.2 mV/K (LTs)/-7.9mV/K (HTs) for I = 10 μA.