Sensitive Metal-Semiconductor Nanothermocouple Fabricated by FIB to Investigate Laser Beams with Nanometer Spatial Resolution.

Adam Łaszcz,Andrzej Czerwinski,Dariusz Szmigiel,Marek Wzorek,Emilia Pruszyńska-Karbownik

doi:10.3390/s22010287

Abstract

The focused ion beam (FIB) technique was used to fabricate a nanothermocouple (with a 90 nm wide nanojunction) based on a metal–semiconductor (Pt–Si) structure, which showed a sensitivity up to 10 times larger (with Seebeck coefficient up to 140 µV/K) than typical metal–metal nanothermocouples. In contrast to the fabrication of nanothermocouples which requires a high-tech semiconductor manufacturing line with sophisticated fabrication techniques, environment, and advanced equipment, FIB systems are available in many research laboratories without the need for a high-tech environment, and the described processing is performed relatively quickly by a single operator. The linear response of the manufactured nanothermocouple enabled sensitive measurements even with small changes of temperature when heated with a stream of hot air. A nonlinear response of the nanothermocouple (up to 83.85 mV) was observed during the exposition to an argon-laser beam with a high optical power density (up to 17.4 Wcm−2), which was also used for the laser annealing of metal–semiconductor interfaces. The analysis of the results implies the application of such nanothermocouples, especially for the characterization of laser beams with nanometer spatial resolution. Improvements of the FIB processing should lead to an even higher Seebeck coefficient of the nanothermocouples; e.g., in case of the availability of other suitable metal sources (e.g., Cr).

Highlights

Thermocouples are widely used as components of infrared sensors, thermal probes, motion sensors, energy generators, complex systems based on MEMS/NEMS structures, and many others [1,2,3,4,5,6]
For the thermoelectric energy conversion of thermal energy transforms to electricity, the maximum efficiency is determined by the dimensionless figure of merit (ZT) for the chosen thermoelectric materials, which is given by ZT = S2σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the temperature
The research aimed at manufacturing a metal–semiconductor (Pt–Si) nano couple by the focused ion beam (FIB) technique and determining the level of its thermoelectric respo obtained results confirmed that the nanothermocouple can be suitable for the laser beams with a nanometer spatial resolution and high ssensitivity (10 times be for metal–metal nanostructures)

Summary

Introduction

Thermocouples are widely used as components of infrared sensors, thermal probes, motion sensors, energy generators, complex systems based on MEMS/NEMS structures, and many others [1,2,3,4,5,6]. The main advantage of thermoelectric measurement systems based on nanostructures is their very high spatial and time resolution of measurements in comparison to conventional macro or microsystems, because larger structures average the results both in space and time. This is important in scientific applications and especially useful for the characterization of laser radiation, where usually microscale devices have been used so far [1,7]. Is increased by the high Seebeck coefficient as well as the low thermal conductivity and electrical resistivity of materials used for thermocouples [8]. In this study, we investigate the possibility of application of thermoelectric materials with high values of the Seebeck coefficient (e.g., semiconductors), shaped in the form of nanostructures

Methods

Results

Conclusion