KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 4 of 4

Some of the metrics are blocked by your
consent settings
Comparison of thermoelectric properties of flexible bismuth telluride thin films deposited via DC and RF magnetron sputtering
(2019-11-18)
Jitthamapirom, Piya
;
Wanarattikan, Pornsiri
;
Nuthongkum, Pilaipon
;
Sakdanuphab, Rachsak
;
Sakulkalavek, Aparporn
Bi<inf>2</inf>Te<inf>3</inf> thin films were deposited onto polyamide sheets with direct current (DC) or radio frequency (RF) magnetron sputtering techniques. The films were prepared using a Bi<inf>2</inf>Te<inf>3</inf> target at a varying pre-heating temperature from 150 to 350 °C. It was observed that the type of plasma excitation and pre-heating temperature can significantly change the composition, preferred orientation, crystallinity, and thermoelectric properties of the films. The pre-heat treatment significantly affected the non-stoichiometric composition. In addition, it was shown that crystallinity and (0 0 l) planes were enhanced in the DC sputtered coatings at a high pre-heating temperature. The maximum power factor of 3.5 × 10−3 W/m K2 at 285 °C was obtained for the films deposited using DC magnetron sputtering and a pre-heating temperature of 350 °C. The carrier concentration and mobility of the film were 5.40 × 1020 cm−3 and 13.04 cm2/V s, respectively. Compared with an ordinary Bi<inf>2</inf>Te<inf>3</inf> film, the power factor of such film has been greatly increased. The results indicated that DC magnetron sputtering can enhance the (0 0l) plane orientation in the Bi<inf>2</inf>Te<inf>3</inf> film.
Some of the metrics are blocked by your
consent settings
[Bi]:[Te] Control, Structural and Thermoelectric Properties of Flexible BixTey Thin Films Prepared by RF Magnetron Sputtering at Different Sputtering Pressures
(2017-11-01)
Nuthongkum, Pilaipon
;
Sakdanuphab, Rachsak
;
Horprathum, Mati
;
Sakulkalavek, Aparporn
In this work, flexible Bi<inf>x</inf>Te<inf>y</inf> thin films were prepared by radio frequency (RF) magnetron sputtering using a Bi<inf>2</inf>Te<inf>3</inf> target on polyimide substrate. The effects of sputtering pressures, which ranged between 0.6 Pa and 1.6 Pa on the [Bi]:[Te] ratio, and structural and thermoelectric properties were investigated. The [Bi]:[Te] ratio of thin film was determined by energy-dispersive spectrometry (EDS). The EDS spectra show the variation of the [Bi]:[Te] ratio as the sputtering pressure is varied. The film deposited at 1.4 Pa almost has a stoichiometric composition. The selective films with different [Bi]:[Te] ratios and sputtering pressures were characterized by their surface morphologies, crystal and chemical structures by field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD) and Raman spectroscopy, respectively. Electrical transport properties, including carrier concentration and mobility, were measured by Hall effect measurements. Seebeck coefficients and electrical conductivities were simultaneously measured by a direct current four-terminal method (ZEM-3). The XRD and Raman spectroscopy results show a difference in microstructure between BiTe and Bi<inf>2</inf>Te<inf>3</inf> depending on the [Bi]:[Te] ratio. Electrical conductivity and Seebeck coefficient are related to the crystal and chemical structures. The maximum power factor of the Bi<inf>2</inf>Te<inf>3</inf> thin film is 9.5 × 10−4 W/K2 m at room temperature, and it increases to 12.0 × 10−4 W/K2 m at 195°C.
Some of the metrics are blocked by your
consent settings
Effects of annealing temperature on the structural, mechanical and electrical properties of flexible bismuth telluride thin films prepared by high-pressure RF magnetron sputtering
(2017-09-01)
Singkaselit, Kamolmad
;
Sakulkalavek, Aparporn
;
Sakdanuphab, Rachsak
In this work BixTey thin films were deposited on polyimide substrate by a high-pressure RF magnetron sputtering technique. The deposited condition was maintained using a high pressure of 1.3 × 10-2 mbar. The as-deposited films show Bi<inf>2</inf>Te<inf>3</inf> structure with Te excess phase (Te-rich Bi<inf>2</inf>Te<inf>3</inf>). After that, as-deposited films were annealed in the vacuum chamber under the N<inf>2</inf> flow at temperatures from 250 to 400 °C for one hour. The microstructure, cross-section, [Bi]:[Te] content, and the mechanical, electrical and thermoelectric properties of as-deposited and different annealed films were investigated. It was found that the annealing temperature enhanced the crystallinity and film density for the temperature range 250-300 °C. However, the crystal structure of Bi<inf>2</inf>Te<inf>3</inf> almost changed to the BiTe structure after annealing the films above 350 °C, due to the re-evaporation of Te. Nano-indentation results and cross-section images indicated that the hardness of the films related to the film density. The maximum hardness of 2.30 GPa was observed by annealing the films at 300 °C. As a result of an improvement in crystallinity and phase changes, the highest power factor of 11.45 × 10-4 W m-1K-2 at 300 °C with the carrier concentration and mobility of 6.15 × 1020 cm-3 and 34.03cm2 V-1 s-1, respectively, was achieved for the films annealed at 400 °C.
Some of the metrics are blocked by your
consent settings
RSM Base Study of the Effect of Argon Gas Flow Rate and Annealing Temperature on the [Bi]:[Te] Ratio and Thermoelectric Properties of Flexible Bi-Te Thin Film
(2017-05-01)
Nuthongkum, Pilaipon
;
Sakulkalavek, Aparporn
;
Sakdanuphab, Rachsak
Bismuth telluride (Bi-Te) thin films coated on a flexible substrate were prepared by RF (radio frequency) magnetron sputtering technique. A response surface methodology based on a central composite design was used to optimize deposition parameters, including the amount of Ar gas flow rate (100.5–106.5 sccm) in the sputtering process and the annealing temperature (250–320°C) for stoichiometric Bi<inf>2</inf>Te<inf>3</inf> thin films. The mathematical model was validated and proven to be statistically sufficient and accurate in predicting a response (Te content). The stoichiometric Bi<inf>2</inf>Te<inf>3</inf> thin films can be prepared on terms appropriate to the Ar flow rate and annealing temperature under several conditions, such as at the Ar flow rate of 103.5 sccm followed by an annealing temperature of 285°C. The characterization of the crystal structure and surface morphology of selected samples with different [Bi]:[Te] content were analyzed by x-ray diffraction (XRD) and a field emission scanning electron microscope, respectively. The XRD spectra showed Bi-Te and Bi<inf>2</inf>Te<inf>3</inf> structures that corresponded with the ratio of [Bi]:[Te]. The Seebeck coefficient and electrical conductivity were simultaneously measured at room temperature and up to 300°C by a direct current four-terminal method. The maximum power factor of the stoichiometric Bi<inf>2</inf>Te<inf>3</inf> thin film was 61×10−5 W/K2m at 243°C.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results