scholarly journals Formation and Evaluation of Silicon Substrate with Highly-Doped Porous Si Layers Formed by Metal-Assisted Chemical Etching

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yijie Li ◽  
Nguyen Van Toan ◽  
Zhuqing Wang ◽  
Khairul Fadzli Bin Samat ◽  
Takahito Ono
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Contact Resistance ◽  
Power Factor ◽  
Chemical Etching ◽  
Porous Si ◽  
Si Substrate ◽  
Si Substrates ◽  
Output Performance ◽  
Metal Assisted Chemical Etching

AbstractPorous silicon (Si) is a low thermal conductivity material, which has high potential for thermoelectric devices. However, low output performance of porous Si hinders the development of thermoelectric performance due to low electrical conductivity. The large contact resistance from nonlinear contact between porous Si and metal is one reason for the reduction of electrical conductivity. In this paper, p- and n-type porous Si were formed on Si substrate by metal-assisted chemical etching. To decrease contact resistance, p- and n-type spin on dopants are employed to dope an impurity element into p- and n-type porous Si surface, respectively. Compared to the Si substrate with undoped porous samples, ohmic contact can be obtained, and the electrical conductivity of doped p- and n-type porous Si can be improved to 1160 and 1390 S/m, respectively. Compared with the Si substrate, the special contact resistances for the doped p- and n-type porous Si layer decreases to 1.35 and 1.16 mΩ/cm2, respectively, by increasing the carrier concentration. However, the increase of the carrier concentration induces the decline of the Seebeck coefficient for p- and n-type Si substrates with doped porous Si samples to 491 and 480 μV/K, respectively. Power factor is related to the Seebeck coefficient and electrical conductivity of thermoelectric material, which is one vital factor that evaluates its output performance. Therefore, even though the Seebeck coefficient values of Si substrates with doped porous Si samples decrease, the doped porous Si layer can improve the power factor compared to undoped samples due to the enhancement of electrical conductivity, which facilitates its development for thermoelectric application.

scholarly journals Preparation and Thermoelectric Properties of Graphite/poly(3,4-ethyenedioxythiophene) Nanocomposites

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2849 ◽  
Author(s):  
Yong Du ◽  
Haixia Li ◽  
Xuechen Jia ◽  
Yunchen Dou ◽  
Jiayue Xu ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Oxidative Polymerization ◽  
Polymerization Process ◽  
Measurement Temperature ◽  
Temperature Range ◽  
Different Content

Graphite/poly(3,4-ethyenedioxythiophene) (PEDOT) nanocomposites were prepared by an in-situ oxidative polymerization process. The electrical conductivity and Seebeck coefficient of the graphite/PEDOT nanocomposites with different content of graphite were measured in the temperature range from 300 K to 380 K. The results show that as the content of graphite increased from 0 to 37.2 wt %, the electrical conductivity of the nanocomposites increased sharply from 3.6 S/cm to 80.1 S/cm, while the Seebeck coefficient kept almost the same value (in the range between 12.0 μV/K to 15.1 μV/K) at 300 K, which lead to an increased power factor. The Seebeck coefficient of the nanocomposites increased from 300 K to 380 K, while the electrical conductivity did not substantially depend on the measurement temperature. As a result, a power factor of 3.2 μWm−1 K−2 at 380 K was obtained for the nanocomposites with 37.2 wt % graphite.

scholarly journals Annealing Effect on the Thermoelectric Properties of Bi2Te3Thin Films Prepared by Thermal Evaporation Method

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Jyun-Min Lin ◽  
Ying-Chung Chen ◽  
Chi-Pi Lin
Keyword(s):  
Thin Films ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Thermal Evaporation ◽  
Thermal Evaporation Method ◽  
Si Substrates ◽  
Seebeck Coefficients

Bismuth telluride-based compounds are known to be the best thermoelectric materials within room temperature region, which exhibit potential applications in cooler or power generation. In this paper, thermal evaporation processes were adopted to fabricate the n-type Bi2Te3thin films on SiO2/Si substrates. The influence of thermal annealing on the microstructures and thermoelectric properties of Bi2Te3thin films was investigated in temperature range 100–250°C. The crystalline structures and morphologies were characterized by X-ray diffraction and field emission scanning electron microscope analyses. The Seebeck coefficients, electrical conductivity, and power factor were measured at room temperature. The experimental results showed that both the Seebeck coefficient and power factor were enhanced as the annealing temperature increased. When the annealing temperature increased to 250°C for 30 min, the Seebeck coefficient and power factor of n-type Bi2Te3-based thin films were found to be about −132.02 μV/K and 6.05 μW/cm·K2, respectively.

scholarly journals Influence of crystallinity on the thermoelectric power factor of P3HT vapour-doped with F4TCNQ

RSC Advances ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 1593-1599 ◽  
Author(s):  
Jonna Hynynen ◽  
David Kiefer ◽  
Christian Müller
Keyword(s):  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Thermoelectric Power Factor ◽  
Order Of Magnitude

The crystallinity of P3HT strongly benefits the electrical conductivity but not Seebeck coefficient, leading to an increase in power factor by one order of magnitude.

Carbon nanotubes enhanced Seebeck coefficient and power factor of rutile TiO2

2015 ◽  
Vol 17 (12) ◽  
pp. 8120-8124 ◽  
Author(s):  
Yao-Cheng Lai ◽  
Hsin-Jung Tsai ◽  
Chia-I Hung ◽  
Hiroyuki Fujishiro ◽  
Tomoyuki Naito ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Filling Fraction ◽  
Rutile Tio2

Ti–C substitution occurs when carbon nanotubes were thermally dispersed in rutile TiO2 and the electrical conductivity as well as Seebeck coefficient were simultaneously promoted at a low filling fraction of tubes.

TEXTURED STRUCTURE AND ANISOTROPIC THERMOELECTRIC PROPERTIES OF Ca2.7Bi0.3Co4O9 OXIDE PREPARED BY CONVENTIONAL SOLID-STATE REACTION

2009 ◽  
Vol 23 (01) ◽  
pp. 87-95 ◽  
Author(s):  
HAOSHAN HAO ◽  
QINGLIN HE ◽  
CHANGQING CHEN ◽  
HONGWEI SUN ◽  
XING HU
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Solid State ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Solid State Reaction ◽  
Solid State Reaction Method ◽  
Conventional Solid State Reaction ◽  
Reaction Method ◽  
Bi Doping

Ca 3-x Bi x Co 4 O 9(x = 0.0, 0.3) samples have been prepared at 1223 K by conventional solid-state reaction method. XRD and SEM investigations reveal that c-axis-oriented structure could be formed in Ca 2.7 Bi 0.3 Co 4 O 9 samples, whereas grains in Ca 3 Co 4 O 9 samples distribute randomly. Moreover, Bi doping increases the grain size and relative density of Ca 2.7 Bi 0.3 Co 4 O 9. The electrical conductivity along the ab plane for Ca 2.7 Bi 0.3 Co 4 O 9 is about four times as large as that along the c-axis, but the Seebeck coefficient is almost isotropic, which leads to a remarkable rise of the power factor in ab plane for Ca 2.7 Bi 0.3 Co 4 O 9 compared with untextured Ca 3 Co 4 O 9. The textured structure in Ca 2.7 Bi 0.3 Co 4 O 9 sample should be attributed to the effect of Bi doping.

scholarly journals Heterogeneous optoelectronic characteristics of Si micropillar arrays fabricated by metal-assisted chemical etching

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yang Qian ◽  
David J. Magginetti ◽  
Seokmin Jeon ◽  
Yohan Yoon ◽  
Tony L. Olsen ◽  
...  
Keyword(s):  
Surface Potential ◽  
Chemical Etching ◽  
High Surface ◽  
Electrochemical Reactions ◽  
Objective Lens ◽  
Chemical Compositions ◽  
Porous Structures ◽  
Porous Si ◽  
Metal Assisted Chemical Etching ◽  
Micropillar Arrays

Abstract Recent progress achieved in metal-assisted chemical etching (MACE) has enabled the production of high-quality micropillar arrays for various optoelectronic applications. Si micropillars produced by MACE often show a porous Si/SiOx shell on crystalline pillar cores introduced by local electrochemical reactions. In this paper, we report the distinct optoelectronic characteristics of the porous Si/SiOx shell correlated to their chemical compositions. Local photoluminescent (PL) images obtained with an immersion oil objective lens in confocal microscopy show a red emission peak (≈ 650 nm) along the perimeter of the pillars that is threefold stronger compared to their center. On the basis of our analysis, we find an unexpected PL increase (≈ 540 nm) at the oil/shell interface. We suggest that both PL enhancements are mainly attributed to the porous structures, a similar behavior observed in previous MACE studies. Surface potential maps simultaneously recorded with topography reveal a significantly high surface potential on the sidewalls of MACE-synthesized pillars (+ 0.5 V), which is restored to the level of planar Si control (− 0.5 V) after removing SiOx in hydrofluoric acid. These distinct optoelectronic characteristics of the Si/SiOx shell can be beneficial for various sensor architectures.

Comparison of the GaAs Layers Grown on Porous Si and on Si by Molecular Beam Epitaxy

1989 ◽  
Vol 145 ◽  
Author(s):  
B.J. Wu ◽  
K.L. Wang ◽  
Y.J. Mii ◽  
Y.S. Yoon ◽  
A.T. Wu ◽  
...  
Keyword(s):  
Residual Stress ◽  
Molecular Beam Epitaxy ◽  
Dislocation Density ◽  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Molecular Beam ◽  
Porous Si ◽  
Si Substrate ◽  
Si Substrates

AbstractGaAs layers have been successfully grown on tilted (100) Si as well as porous Si substrates by molecular beam epitaxy(MBE). Rapid thermal annealing and vacuum thermal annealing have been used to further improve the quality of the epitaxial layers. We observed that the dislocation density near the interface of the heterostructure is higher for GaAs on Si substrate. Both annealing processes are proven to be useful in improving layer quality, while the vacuum thermal annealing seemed to be more effective in minimizing the residual stress.

Catalyst feature independent metal-assisted chemical etching of silicon

RSC Advances ◽  
2015 ◽  
Vol 5 (93) ◽  
pp. 76128-76132 ◽  
Author(s):  
Keorock Choi ◽  
Yunwon Song ◽  
Ilwhan Oh ◽  
Jungwoo Oh
Keyword(s):  
Chemical Etching ◽  
Metal Catalysts ◽  
Si Substrates ◽  
Wide Range ◽  
Metal Assisted Chemical Etching

We demonstrate metal-assisted chemical etching of Si substrates with consistent etching rates for a wide range of metal catalysts of dots and stripes in meshes and solid arrays.

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