Pub Date : 2024-11-07DOI: 10.1007/s13391-024-00527-7
BeomSoo Kim, Hyungyu Cho, Okmin Park, Seungchan Seon, Sang-il Kim
Metal chalcogenides are widely studied as thermoelectric materials due to their finely tunable electronic transport properties over a wide temperature range. FeSe2 has recently been considered a promising thermoelectric material with investigations focusing on restraining bipolar behavior through doping. In this study, a series of Cl-doped FeSe2 compositions, a series of FeSe2 − xClx (x = 0, 0.01, 0.025, and 0.05) compositions, were synthesized to investigate the influence of Cl doping. While the gradually decreasing lattice parameters with doping content x suggests successful doping up to x = 0.05, the hole concentration slightly decreased owing to electrons generated by the Cl doping. Nevertheless, the electrical conductivity and Seebeck coefficient show no systematic change with x owing to very low electron generating efficiency, and no distinctive enhancement of power factor is seen for the doped samples. On the other hand, the lattice thermal conductivity gradually and significantly decreased with x from 9.2 W/mK to 6.3 W/mK for x = 0.05 by 32% at 300 K, which is originated from the effective additional phonon scattering due to the difference in mass (55%) and size (9%) between Se2− and Cl− ions. Consequently, a thermoelectric figure of merit is increased to 0.073 from 0.057 at 600 K for x = 0.05.
{"title":"Enhanced Thermoelectric Properties of FeSe2 Alloys by Lattice Thermal Conductivity Reduction by Cl Doping","authors":"BeomSoo Kim, Hyungyu Cho, Okmin Park, Seungchan Seon, Sang-il Kim","doi":"10.1007/s13391-024-00527-7","DOIUrl":"10.1007/s13391-024-00527-7","url":null,"abstract":"<div><p>Metal chalcogenides are widely studied as thermoelectric materials due to their finely tunable electronic transport properties over a wide temperature range. FeSe<sub>2</sub> has recently been considered a promising thermoelectric material with investigations focusing on restraining bipolar behavior through doping. In this study, a series of Cl-doped FeSe<sub>2</sub> compositions, a series of FeSe<sub>2 − x</sub>Cl<sub>x</sub> (<i>x</i> = 0, 0.01, 0.025, and 0.05) compositions, were synthesized to investigate the influence of Cl doping. While the gradually decreasing lattice parameters with doping content <i>x</i> suggests successful doping up to <i>x</i> = 0.05, the hole concentration slightly decreased owing to electrons generated by the Cl doping. Nevertheless, the electrical conductivity and Seebeck coefficient show no systematic change with <i>x</i> owing to very low electron generating efficiency, and no distinctive enhancement of power factor is seen for the doped samples. On the other hand, the lattice thermal conductivity gradually and significantly decreased with <i>x</i> from 9.2 W/mK to 6.3 W/mK for <i>x</i> = 0.05 by 32% at 300 K, which is originated from the effective additional phonon scattering due to the difference in mass (55%) and size (9%) between Se<sup>2−</sup> and Cl<sup>−</sup> ions. Consequently, a thermoelectric figure of merit is increased to 0.073 from 0.057 at 600 K for <i>x</i> = 0.05.</p><h3>Graphical Abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":536,"journal":{"name":"Electronic Materials Letters","volume":"21 1","pages":"79 - 86"},"PeriodicalIF":2.1,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-15DOI: 10.1007/s13391-024-00526-8
Minah Park, Jaewook Yoo, Hongseung Lee, Hyeonjun Song, Soyeon Kim, Seongbin Lim, Seohyeon Park, Jo Hak Jeong, Bongjoong Kim, Kiyoung Lee, Yoon Kyeung Lee, Keun Heo, Jiseok Kwon, Hagyoul Bae
Amorphous indium-gallium-zinc-oxide (a-IGZO) has been attracting great attention as a channel material for dynamic random access memory (DRAM) cell transistors due to its superior characteristics including low leakage current, large area deposition, and back-end-of-line (BEOL) compatibility. It should be clearly taken into account that DRAM will also be used in harsh environments such as military surveillance, aerospace, and nuclear power plants. Especially, these situations can cause inevitable and persistent degradation in long-term operations. When the a-IGZO thin film transistors (TFTs) were irradiated by gamma-ray with total doses of 500 Gy, threshold voltage (VT) was negatively shifted and hysteresis (delta of VT between forward and backward sweeps) was increased by creating a positive charge in gate insulator. The extracted density-of-states (DOS) and fitted model were employed to investigate the behavior of oxygen vacancy (VO) in a-IGZO thin film. Electrical performance degraded by gamma-ray irradiation such as changes in VT, border trap, tail acceptor-like states (gTA(E)), and shallow donor-like states (gSD(E)) were recovered through rapid thermal annealing (RTA) under the O2 ambient.
{"title":"Rapid Thermal Annealing under O2 Ambient to Recover the Deterioration by Gamma-Ray Irradiation in a-IGZO TFTs","authors":"Minah Park, Jaewook Yoo, Hongseung Lee, Hyeonjun Song, Soyeon Kim, Seongbin Lim, Seohyeon Park, Jo Hak Jeong, Bongjoong Kim, Kiyoung Lee, Yoon Kyeung Lee, Keun Heo, Jiseok Kwon, Hagyoul Bae","doi":"10.1007/s13391-024-00526-8","DOIUrl":"10.1007/s13391-024-00526-8","url":null,"abstract":"<div><p>Amorphous indium-gallium-zinc-oxide (a-IGZO) has been attracting great attention as a channel material for dynamic random access memory (DRAM) cell transistors due to its superior characteristics including low leakage current, large area deposition, and back-end-of-line (BEOL) compatibility. It should be clearly taken into account that DRAM will also be used in harsh environments such as military surveillance, aerospace, and nuclear power plants. Especially, these situations can cause inevitable and persistent degradation in long-term operations. When the a-IGZO thin film transistors (TFTs) were irradiated by gamma-ray with total doses of 500 Gy, threshold voltage (<i>V</i><sub>T</sub>) was negatively shifted and hysteresis (delta of <i>V</i><sub>T</sub> between forward and backward sweeps) was increased by creating a positive charge in gate insulator. The extracted density-of-states (DOS) and fitted model were employed to investigate the behavior of oxygen vacancy (<i>V</i><sub>O</sub>) in a-IGZO thin film. Electrical performance degraded by gamma-ray irradiation such as changes in <i>V</i><sub>T</sub>, border trap, tail acceptor-like states (<i>g</i><sub>TA</sub>(<i>E</i>)), and shallow donor-like states (<i>g</i><sub>SD</sub>(<i>E</i>)) were recovered through rapid thermal annealing (RTA) under the O<sub>2</sub> ambient.</p><h3>Graphical Abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":536,"journal":{"name":"Electronic Materials Letters","volume":"21 1","pages":"111 - 118"},"PeriodicalIF":2.1,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-10DOI: 10.1007/s13391-024-00524-w
Yu-Jin Song, Changhyeon Yoo, Camellia Schwartzman, Han-Kyun Shin, Hyoung J. Cho, Yeonwoong Jung, Jung Han Kim
WO3/WS2 core/shell nanowires were synthesized using a scalable fabrication method by combining wet chemical etching and chemical vapor deposition (CVD). Initially, WO3 nanowires were formed through wet chemical etching using a potassium hydroxide (KOH) solution, followed by oxidation at 650 °C. These WO3 nanowires were then sulfurized at 900 °C to form a WS2 shell, resulting in WO3/WS2 core/shell nanowires with diameters ranging from 90 to 370 nm. The synthesized nanowires were characterized using scanning electron microscopy (SEM), Raman, energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The shell is composed of 2D WS2 layers with uniformly spaced 2D layers as well as the atomically sharp core/shell interface of WO3/WS2. Notably, the WO3/WS2 heterostructure nanowires exhibited a unique negative photoresponse under visible light (405 nm) illumination. This negative photoresponse highlights the importance of interface engineering in these heterostructures and demonstrates the potential of WO3/WS2 core/shell nanowires for applications in photodetectors and other optoelectronic devices.