Fabrication of Bi2Te3 and Sb2Te3 Thermoelectric Thin Films using Radio Frequency Magnetron Sputtering Technique

Summary

The manuscript describes a protocol for radio frequency magnetron sputtering of Bi₂Te₃ and Sb₂Te₃ thermoelectric thin films on glass substrates, which represents a reliable deposition method that provides a wide range of applications with the potential for further development.

Abstract

Through various studies on thermoelectric (TE) materials, thin film configuration gives superior advantages over conventional bulk TEs, including adaptability to curved and flexible substrates. Several different thin film deposition methods have been explored, yet magnetron sputtering is still favorable due to its high deposition efficiency and scalability. Therefore, this study aims to fabricate a bismuth telluride (Bi₂Te₃) and antimony telluride (Sb₂Te₃) thin film via the radio frequency (RF) magnetron sputtering method. The thin films were deposited on soda lime glass substrates at ambient temperature. The substrates were first washed using water and soap, ultrasonically cleaned with methanol, acetone, ethanol, and deionized water for 10 min, dried with nitrogen gas and hot plate, and finally treated under UV ozone for 10 min to remove residues before the coating process. A sputter target of Bi₂Te₃ and Sb₂Te₃ with Argon gas was used, and pre-sputtering was done to clean the target's surface. Then, a few clean substrates were loaded into the sputtering chamber, and the chamber was vacuumed until the pressure reached 2 x 10^-5 Torr. The thin films were deposited for 60 min with Argon flow of 4 sccm and RF power at 75 W and 30 W for Bi₂Te₃ and Sb₂Te₃, respectively. This method resulted in highly uniform n-type Bi₂Te₃ and p-type Sb₂Te₃ thin films.

Introduction

Thermoelectric (TE) materials have been attracting a considerable amount of research interest regarding their ability to convert thermal energy into electricity via the Seebeck effect¹ and refrigeration via Peltier cooling². The conversion efficiency of TE material is determined by the temperature difference between the hot end of the TE leg and the cold end. Generally, the higher the temperature difference, the higher the TE figure of merit and the higher its efficiency³. TE works with no requirement for additional mechanical parts involving gas or liquid in its process, pro....

Protocol

1. Substrate preparation

1. Wipe the glass substrates with lint-free cloth to remove loose dirt or debris. Wash glass substrates with water and soap, use brush to scrub any dirt on the glass.
2. Prepare all solvents listed below in beakers, submerge the glass substrates in the solvent and sonicate accordingly at 37 kHz. Prepare methanol at 80 °C for 10 min; acetone at 80 °C for 10 min, ethanol at 80 °C for 10 min, distilled (DI) water at 80 °C for 20 min.
   CAUTIO.......

Discussion

The technique presented in this paper presents no significant difficulty in setting up the equipment and implementation. However, several critical steps need to be highlighted. As mentioned in step 2.2.10 of the protocol, optimum vacuum condition is key to produce high quality thin films with less contamination as vacuum removes residual oxygen in the chamber³⁷. The presence of oxygen can cause cracks in the films called stress cracking indicating the importance of high vacuum system in sputtering.......

Materials

Name	Company	Catalog Number	Comments
Acetone	Chemiz (M) Sdn. Bhd.	1910151	Liquid, Flammable
Antimony Telluride, Sb2Te3	China Rare Metal Material Co.,Ltd	C120222-0304	Diameter 50.8 mm, Thickness 6.35 mm, 99.999% purity
Bismuth Telluride, Bi2Te3	China Rare Metal Material Co.,Ltd	CB151208-0501	Diameter 50.8 mm, Thickness 4.25 mm, 99.999% purity
Ethanol	Chemiz (M) Sdn. Bhd.	2007081	Liquid, Flammable
Field Emission Scanning Electron Microscope	Zeiss	MERLIN	Equipped with EDX
Hall effect measurement system	Aseptec Sdn. Bhd.	HMS ECOPIA 3000	-
Handheld digital multimeter	Prokits Industries Sdn. Bhd.	303-150NCS	-
HMS-3000	Aseptec Sdn Bhd.	HMS ECOPIA 3000	Hall effect measurement software
Linseis_TA	Linseis Messgeräte GmbH	LSR-3	Linseis thermal analysis software
Methanol	Chemiz (M) Sdn. Bhd.	2104071	Liquid, Flammable
RF-DC magnetron sputtering	Kurt J. Lesker Company	-	Customized hybrid system
Seebeck coefficient measurement system	Linseis Messgeräte GmbH	LSR-3	-
SmartTiff	Carl Zeiss Microscopy Ltd	-	SEM image thickness measurement software
Ultrasonic bath	Fisherbrand	FB15055	-
UV ozone cleaner	Ossila Ltd	L2002A3-UK	-