A Highly Sensitive Temperature Sensor Based on Au/Graphene-PVP/n-Si Type Schottky Diodes and the Possible Conduction Mechanisms in the Wide Range Temperatures

We report that the sensitive temperature response and possible Conduction Mechanisms (CMs) of Au/graphene-PVP/<inline-formula> <tex-math notation="LaTeX">${n}$ </tex-math></inline-formula>-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 (<inline-formula> <tex-math notation="LaTeX">$\phi _{\textit {Bo}}$ </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">$\phi _{\textit {ap}}$ </tex-math></inline-formula>) increases while the ideality factor (<inline-formula> <tex-math notation="LaTeX">${n}$ </tex-math></inline-formula>), series and shunt resistances (<inline-formula> <tex-math notation="LaTeX">${R} _{s}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">${R} _{\textit {sh}}$ </tex-math></inline-formula>), rectifying rate (at ±2V) and surface states (<inline-formula> <tex-math notation="LaTeX">${N} _{\textit {ss}}$ </tex-math></inline-formula>) decrease with increasing temperature. The <inline-formula> <tex-math notation="LaTeX">$\phi _{\textit {Bo}}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">${n}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">${R} _{s}$ </tex-math></inline-formula> values are also extracted from Cheung’s functions and, then compared with those obtained TE theory. The conventional Richardson plot (<inline-formula> <tex-math notation="LaTeX">$\ell {n}$ </tex-math></inline-formula>(<inline-formula> <tex-math notation="LaTeX">${I} _{o}$ </tex-math></inline-formula> <italic>/T</italic> <sup>2</sup>)-<italic>q/kT</italic>) displays the deviation from the linearity at low-temperatures (<inline-formula> <tex-math notation="LaTeX">$T\le140$ </tex-math></inline-formula> <italic>K). </italic> Besides, the experimental value of Richardson constant (<inline-formula> <tex-math notation="LaTeX">${A} ^{\ast }$ </tex-math></inline-formula>) deduced from the intercept of plot was found to be several orders lower than the theoretical value. The discrepancies and higher values for the parameter of <inline-formula> <tex-math notation="LaTeX">${n}$ </tex-math></inline-formula> 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 <inline-formula> <tex-math notation="LaTeX">${N} _{\textit {ss}}$ </tex-math></inline-formula> 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 (<inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula>) rather than many silicon/SOI-based structures. Numerically, the <inline-formula> <tex-math notation="LaTeX">${S}$ </tex-math></inline-formula> values are found to be in a range of 1.3 mV/K (LTs)/−1.93mV/K (HTs) in case of <inline-formula> <tex-math notation="LaTeX">${I} =0.1\,\,\mu \text{A}$ </tex-math></inline-formula> as against much greater values of −8.2 mV/K (LTs)/−7.9mV/K (HTs) for <inline-formula> <tex-math notation="LaTeX">${I} = 10\,\,\mu \text{A}$ </tex-math></inline-formula>.