A novel langasite crystal microbalance instrumentation for UV sensing application

Abstract In this paper, we present a novel low-power UV sensor instrumentation based on ZnO thin-film and langasite crystal microbalance (LCM) composite resonator. The design of this sensor utilizes the exceptional transient response characteristics of thickness shear mode langasite crystal and UV sensitivity of annealed ZnO thin film. Our comparative transient analysis of langasite and quartz crystals shows that langasite crystal has high stability and fast relaxation times, and requires a fraction of excitation power in comparison to that of quartz. Upon investigating the equivalent circuit components, we discovered that high value of motional capacitance of LCM resulted in these contrasting transient responses in LCM and QCM. This high motional capacitance can be further attributed to the high electromechanical coupling coefficient ( K 2 ) of piezoelectric langasite crystal. Motivated by these observed characteristics, we proposed a novel sensor instrumentation that is simple yet effective in simultaneous measurements of the frequency, dissipation factor, and the amplitude of oscillation of a LCM. Moreover, our measurements allow for direct monitoring of any change in piezoelectricity of ZnO thin film. Our new measurement approach uses a one-shot pulse instead of conventional sinusoidal waveform to drive the crystal, which allows for simple instrumentation and requires very low input power. The transient response of the crystal shows that the crystal oscillates at its fundamental frequency and the amplitude of oscillation decays exponentially. From the recorded decay curve, the frequency of the freely oscillating crystal, and other important crystal parameters were calculated. We have utilized this mechanism to demonstrate highly sensitive ZnO thin film and LCM based UV sensor. Highest sensitivity of 35.8 ppm per μW/cm 2 was observed for the LCM coated with 400 nm ZnO film. Additionally, the influence of UV on the piezoelectric output of ZnO thin film was also characterized by monitoring the DC offset of the output oscillations. Our findings in this work opens scope for developing low-power acoustic sensors with significant implications towards self-powering sensors.

[1]  Teofil Jesionowski,et al.  Zinc Oxide—From Synthesis to Application: A Review , 2014, Materials.

[2]  Xinyu Xue,et al.  Realizing room-temperature self-powered ethanol sensing of ZnO nanowire arrays by combining their piezoelectric, photoelectric and gas sensing characteristics , 2015 .

[3]  W. Dang,et al.  Deposition and characterization of sputtered ZnO films , 2007 .

[4]  Edward T. Zellers,et al.  Chapter 3 – Acoustic Wave Sensors and Responses , 1997 .

[5]  C. Soci,et al.  ZnO nanowire UV photodetectors with high internal gain. , 2007, Nano letters.

[6]  Yicheng Lu,et al.  A ZnO Nanostructure-Based Quartz Crystal Microbalance Device for Biochemical Sensing , 2009, IEEE Sensors Journal.

[7]  Ke Ma,et al.  Performance improvement of ZnO nanowire based surface acoustic wave ultraviolet detector via poly(3,4-ethylenedioxythiophene) surface coating , 2013 .

[8]  G. Sauerbrey,et al.  Use of quartz vibration for weighing thin films on a microbalance , 1959 .

[9]  Holger Fritze,et al.  Langasite for high-temperature acoustic wave gas sensors , 2003 .

[10]  N. Ramakrishnan,et al.  An optimal thermal evaporation synthesis of c-axis oriented ZnO nanowires with excellent UV sensing and emission characteristics , 2016 .

[11]  Tridib Saha,et al.  Zinc Oxide Nanostructure-Based Langasite Crystal Microbalance Ultraviolet Sensor , 2016, IEEE Sensors Journal.

[12]  Bengt Herbert Kasemo,et al.  A simple setup to simultaneously measure the resonant frequency and the absolute dissipation factor of a quartz crystal microbalance , 1996 .

[13]  Nam-Joon Cho,et al.  Quartz Crystal Microbalance as a Sensor to Characterize Macromolecular Assembly Dynamics , 2009, J. Sensors.

[14]  Arlin L. Kipling,et al.  Network analysis method applied to liquid-phase acoustic wave sensors , 1990 .

[15]  Kijung Lee,et al.  Low-intensity ultraviolet detection using a surface acoustic-wave sensor with a Ag-doped ZnO nanoparticle film , 2014 .

[16]  Zhong Lin Wang,et al.  Gigantic enhancement in response and reset time of ZnO UV nanosensor by utilizing Schottky contact and surface functionalization. , 2009, Applied physics letters.

[17]  S. R. Silva,et al.  From 1D and 2D ZnO nanostructures to 3D hierarchical structures with enhanced gas sensing properties. , 2014, Nanoscale.

[18]  Anthony J. Walton,et al.  Love mode surface acoustic wave ultraviolet sensor using ZnO films deposited on 36° Y-cut LiTaO3 , 2013 .

[19]  G. Sauerbrey.  Verwendung von Schwingquarzen zur Wägung dünner Schichten und zur Mikrowägung , 1959 .

[20]  Lili Xing,et al.  Realizing room-temperature self-powered ethanol sensing of Au/ZnO nanowire arrays by coupling the piezotronics effect of ZnO and the catalysis of noble metal , 2014 .

[21]  Fredrik Höök,et al.  Quartz crystal microbalance setup for frequency and Q‐factor measurements in gaseous and liquid environments , 1995 .

[22]  Lifeng Qin,et al.  P1D-2 High Temperature Langasite BAW Gas Sensor Based on ZnO Nanowire Arrays , 2007, 2007 IEEE Ultrasonics Symposium Proceedings.

[23]  Cunjiang Yu,et al.  Film bulk acoustic-wave resonator based ultraviolet sensor , 2009 .

[24]  Qi Kang,et al.  Oscillating frequency response of a langasite crystal microbalance in liquid phases , 2006 .

[25]  Holger Fritze,et al.  Langasite for high-temperature bulk acoustic wave applications , 2001 .

[27]  E. Chilla,et al.  Elastic properties of langasite-type crystals determined by bulk and surface acoustic waves , 2001 .

[28]  S. Dong,et al.  UV sensing using film bulk acoustic resonators based on Au/n-ZnO/piezoelectric-ZnO/Al structure , 2015, Scientific Reports.

[29]  V. Kalavally,et al.  Resonant characteristics and sensitivity dependency on the contact surface in QCM-micropillar-based system of coupled resonator sensors , 2016 .

[30]  Tsung-Tsong Wu,et al.  A ZnO nanorod-based SAW oscillator system for ultraviolet detection , 2009, Nanotechnology.