N. R. Martins, Luiz Augusto Ferreira de Campos Viana, Alan Antônio das Graças Santos, Daiane Damasceno Borges, Eric Welch, P. Borges, L. Scolfaro
Wide band gap semiconductors like gallium oxide are promising materials for high-power optoelectronic device applications. We show here a combined density functional theory and molecular dynamics study of diffusion pathways for different defects in β-Ga2O3. Molecular dynamics simulations result in a smaller equilibrium volume compared to density functional theory, but the overall lattice remains relatively unchanged even with the inclusion of defects, outside of the local distortions that occur to accommodate the presence of a defect. Slight thermal expansion occurs with elevated temperature and a combination of electron localization function and Bader charge analysis reveals that the oxygen interstitial is the most mobile defect as temperature is increased. However, interstitial cations may diffuse at elevated temperature due to a relatively small amount of charge transfer between the defect and lattice. The mobile oxygen defects are shown to increase the mobility of oxygen ions from the lattice, which can be beneficial for electrochemical applications when controlled through annealing processes.
{"title":"Computational study and ion diffusion analyses of native defects and indium alloying in β-Ga2O3 structures","authors":"N. R. Martins, Luiz Augusto Ferreira de Campos Viana, Alan Antônio das Graças Santos, Daiane Damasceno Borges, Eric Welch, P. Borges, L. Scolfaro","doi":"10.1116/6.0003435","DOIUrl":"https://doi.org/10.1116/6.0003435","url":null,"abstract":"Wide band gap semiconductors like gallium oxide are promising materials for high-power optoelectronic device applications. We show here a combined density functional theory and molecular dynamics study of diffusion pathways for different defects in β-Ga2O3. Molecular dynamics simulations result in a smaller equilibrium volume compared to density functional theory, but the overall lattice remains relatively unchanged even with the inclusion of defects, outside of the local distortions that occur to accommodate the presence of a defect. Slight thermal expansion occurs with elevated temperature and a combination of electron localization function and Bader charge analysis reveals that the oxygen interstitial is the most mobile defect as temperature is increased. However, interstitial cations may diffuse at elevated temperature due to a relatively small amount of charge transfer between the defect and lattice. The mobile oxygen defects are shown to increase the mobility of oxygen ions from the lattice, which can be beneficial for electrochemical applications when controlled through annealing processes.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"128 37","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140369780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
So Young Kim, Chunghee Jo, Hyerin Shin, D. Yoon, D. Shin, Min-ho Cheon, Kyu-beom Lee, D. Seo, Jae-wook Choi, Heungsoo Park, Dae-Hong Ko
Challenges have arisen in selecting suitable candidates for interconnects and metal contacts due to the exponential increase in metal resistivity at scaled pitches. Molybdenum (Mo) has emerged as a promising alternative to the traditional metals such as copper or tungsten owing to its low electrical resistivity and electron mean free path. In this study, we investigated the formation of a molybdenum film grown by thermal atomic layer deposition (ALD) using a MoO2Cl2 solid precursor and H2 and NH3 gases as the reducing agents. A molybdenum nitride film served as the seed layer on a SiO2 substrate before molybdenum film deposition. The analysis focused on the film's phase, morphology, chemical bonding states, and resistivity across various thicknesses. X-ray diffraction (XRD) confirmed the presence of polycrystalline BCC planes. Our analyses confirmed the successful growth of the molybdenum metal thin film, which, at a thickness of 10 nm, exhibited a record-low resistivity of approximately 13 μΩ cm.
{"title":"Properties of low-resistivity molybdenum metal thin film deposited by atomic layer deposition using MoO2Cl2 as precursor","authors":"So Young Kim, Chunghee Jo, Hyerin Shin, D. Yoon, D. Shin, Min-ho Cheon, Kyu-beom Lee, D. Seo, Jae-wook Choi, Heungsoo Park, Dae-Hong Ko","doi":"10.1116/6.0003361","DOIUrl":"https://doi.org/10.1116/6.0003361","url":null,"abstract":"Challenges have arisen in selecting suitable candidates for interconnects and metal contacts due to the exponential increase in metal resistivity at scaled pitches. Molybdenum (Mo) has emerged as a promising alternative to the traditional metals such as copper or tungsten owing to its low electrical resistivity and electron mean free path. In this study, we investigated the formation of a molybdenum film grown by thermal atomic layer deposition (ALD) using a MoO2Cl2 solid precursor and H2 and NH3 gases as the reducing agents. A molybdenum nitride film served as the seed layer on a SiO2 substrate before molybdenum film deposition. The analysis focused on the film's phase, morphology, chemical bonding states, and resistivity across various thicknesses. X-ray diffraction (XRD) confirmed the presence of polycrystalline BCC planes. Our analyses confirmed the successful growth of the molybdenum metal thin film, which, at a thickness of 10 nm, exhibited a record-low resistivity of approximately 13 μΩ cm.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"52 17","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140376599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Aonuki, Kaori Takayanagi, Ai Iwai, K. Toko, T. Suemasu
Epitaxial growth of BaSi2 films on Si(111) has demonstrated that the BaSi2 template can serve as a seed crystal for BaSi2 overlayers by molecular beam epitaxy (MBE) and shows high photoresponsivity, but not yet on Ge(111) substrates. We have investigated the effect of various templates on the photoresponsivity of BaSi2 films grown on Ge(111) substrates. Samples with MBE-grown templates exhibited high a-axis orientation, but the surface was uneven, leading to partial oxidation of the BaSi2 film. On the other hand, the sample without such templates showed a smoother surface but was confirmed to be polycrystalline. When a template formed by the combination of solid phase epitaxy (SPE) and subsequent annealing for 30 min was used, a-axis-oriented BaSi2 together with 111-oriented Si appeared in the θ–2θ x-ray diffraction (XRD) patterns. The fact that no crystalline Si was detected by the surface-sensitive Raman spectroscopy and that the full width at half maximum of the XRD BaSi2 600 peak was increased to 2.686° in such samples suggests that Si aggregates were at the BaSi2/Ge interface. The photoresponsivity of the epitaxial BaSi2 film with MBE-grown templates reached 0.14 A W−1 at a wavelength of 790 nm. This is the highest photoresponsivity reported so far for BaSi2 films on Ge substrates. Even for samples without the MBE-grown templates, SPE-grown templates significantly increased the photoresponsivity up to 0.10 A W−1. These results confirm that the template has a significant impact on the photoresponsivity of BaSi2 films on Ge(111) substrates.
在硅(111)基底上外延生长的 BaSi2 薄膜已经证明，BaSi2 模板可以作为分子束外延 (MBE) 的 BaSi2 叠层的籽晶，并显示出很高的光致发射率，但在 Ge(111) 基底上还没有显示出来。我们研究了各种模板对在 Ge(111) 基质上生长的 BaSi2 薄膜光致发光率的影响。使用 MBE 生长模板的样品具有较高的 a 轴取向性，但表面不平整，导致 BaSi2 薄膜部分氧化。另一方面，没有此类模板的样品表面更光滑，但已确认为多晶。当使用固相外延（SPE）和随后的 30 分钟退火相结合形成的模板时，θ-2θ X 射线衍射（XRD）图中出现了面向 a 轴的 BaSi2 和面向 111 轴的 Si。表面敏感拉曼光谱检测不到结晶硅，而且在这些样品中，X 射线衍射 BaSi2 600 峰的半最大全宽增加到 2.686°，这表明硅聚集在 BaSi2/Ge 界面上。采用 MBE 生长模板的外延 BaSi2 薄膜在波长为 790 纳米时的光致发光率达到 0.14 A W-1。这是迄今为止报告的 Ge 基底上的 BaSi2 薄膜的最高光致反射率。即使是没有 MBE 生长模板的样品，SPE 生长模板也能显著提高光致反射率，最高可达 0.10 A W-1。这些结果证实，模板对 Ge（111）衬底上的 BaSi2 薄膜的光致发光率有重大影响。
{"title":"Effect of template on the photoresponsivity of BaSi2 films grown on Ge(111) substrates by molecular beam epitaxy","authors":"S. Aonuki, Kaori Takayanagi, Ai Iwai, K. Toko, T. Suemasu","doi":"10.1116/6.0003503","DOIUrl":"https://doi.org/10.1116/6.0003503","url":null,"abstract":"Epitaxial growth of BaSi2 films on Si(111) has demonstrated that the BaSi2 template can serve as a seed crystal for BaSi2 overlayers by molecular beam epitaxy (MBE) and shows high photoresponsivity, but not yet on Ge(111) substrates. We have investigated the effect of various templates on the photoresponsivity of BaSi2 films grown on Ge(111) substrates. Samples with MBE-grown templates exhibited high a-axis orientation, but the surface was uneven, leading to partial oxidation of the BaSi2 film. On the other hand, the sample without such templates showed a smoother surface but was confirmed to be polycrystalline. When a template formed by the combination of solid phase epitaxy (SPE) and subsequent annealing for 30 min was used, a-axis-oriented BaSi2 together with 111-oriented Si appeared in the θ–2θ x-ray diffraction (XRD) patterns. The fact that no crystalline Si was detected by the surface-sensitive Raman spectroscopy and that the full width at half maximum of the XRD BaSi2 600 peak was increased to 2.686° in such samples suggests that Si aggregates were at the BaSi2/Ge interface. The photoresponsivity of the epitaxial BaSi2 film with MBE-grown templates reached 0.14 A W−1 at a wavelength of 790 nm. This is the highest photoresponsivity reported so far for BaSi2 films on Ge substrates. Even for samples without the MBE-grown templates, SPE-grown templates significantly increased the photoresponsivity up to 0.10 A W−1. These results confirm that the template has a significant impact on the photoresponsivity of BaSi2 films on Ge(111) substrates.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"5 21","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140374942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jeremiah Williams, Weisong Wang, N. Hendricks, Aaron Adams, Joshua Piel, D. Dryden, K. Liddy, N. Sepelak, Bradley Morell, A. Islam, Andrew J. Green
This work demonstrates TiO2/β-Ga2O3 metal–dielectric–semiconductor (MDS) diodes with an average breakdown field beyond the material limits of SiC and GaN. These MDS diodes have lower conduction losses and higher breakdown voltage (Vbk) than the cofabricated Schottky barrier diodes (SBDs), simultaneously improving both on- and off-state parameters that are typically in competition with each other. With further optimized field management using p-NiO guard rings (GRs), the Ni/TiO2/β-Ga2O3 MDS diodes present a path to realistically utilize the high critical field of Ga2O3 without large forward conduction losses from a high-barrier junction. MDS diodes showed a lower Von (0.8 V) than the SBDs (1.1 V) from linear extrapolation of the current density-voltage (J-V) curve. The MDS diode had higher Vbk of 1190 V (3.0 MV/cm) compared to 685 V (2.3 MV/cm) for the SBD, and the MDS diode with the p-NiO guard ring saw further improvement with Vbk of 1776 V (3.7 MV/cm) compared to 826 V (2.5 MV/cm) for GR SBD. The BFOM (Vbk2/Ron,sp) of 518 MW/cm2 for the GR HJD is competitive with other literature results. A new figure of merit that includes the impact of turn on voltage is also proposed and demonstrated in this paper, which highlights how diodes perform in a practical high-power operation. This full paper is derived from the proceeding abstract of Willams et al. [IEEE Device Research Conference, Santa Barbara, CA, 25-28 June 2023 (IEEE, New York, 2023)].
{"title":"Experimental study of Ni/TiO2/β-Ga2O3 metal–dielectric–semiconductor diodes using p-NiO junction termination extension","authors":"Jeremiah Williams, Weisong Wang, N. Hendricks, Aaron Adams, Joshua Piel, D. Dryden, K. Liddy, N. Sepelak, Bradley Morell, A. Islam, Andrew J. Green","doi":"10.1116/6.0003467","DOIUrl":"https://doi.org/10.1116/6.0003467","url":null,"abstract":"This work demonstrates TiO2/β-Ga2O3 metal–dielectric–semiconductor (MDS) diodes with an average breakdown field beyond the material limits of SiC and GaN. These MDS diodes have lower conduction losses and higher breakdown voltage (Vbk) than the cofabricated Schottky barrier diodes (SBDs), simultaneously improving both on- and off-state parameters that are typically in competition with each other. With further optimized field management using p-NiO guard rings (GRs), the Ni/TiO2/β-Ga2O3 MDS diodes present a path to realistically utilize the high critical field of Ga2O3 without large forward conduction losses from a high-barrier junction. MDS diodes showed a lower Von (0.8 V) than the SBDs (1.1 V) from linear extrapolation of the current density-voltage (J-V) curve. The MDS diode had higher Vbk of 1190 V (3.0 MV/cm) compared to 685 V (2.3 MV/cm) for the SBD, and the MDS diode with the p-NiO guard ring saw further improvement with Vbk of 1776 V (3.7 MV/cm) compared to 826 V (2.5 MV/cm) for GR SBD. The BFOM (Vbk2/Ron,sp) of 518 MW/cm2 for the GR HJD is competitive with other literature results. A new figure of merit that includes the impact of turn on voltage is also proposed and demonstrated in this paper, which highlights how diodes perform in a practical high-power operation. This full paper is derived from the proceeding abstract of Willams et al. [IEEE Device Research Conference, Santa Barbara, CA, 25-28 June 2023 (IEEE, New York, 2023)].","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"107 32","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140380584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carlos Ramos, Daniela S. Jacobo-Mora, J. Cruz, Stephen Muhl
Recently, there has been increasing interest in the use of hot targets to enhance the sputter deposition of materials. However, the actual temperature of the target surface is normally not known. In this work, we directly measured the radial distribution of the surface temperature of a MAK 2 in. Ti water-cooled target using a type K thermocouple during the operation of the sputtering system. Principally, the measurements were made as a function of applied DC power and argon gas pressure. Given the importance of chemical reactions between the gas and the target during reactive sputtering, we have also measured the target temperature as a function of the nitrogen concentration in an argon-nitrogen gas mixture. A few of the reactively sputtered samples were analyzed by x-ray photoelectron spectroscopy.
最近，人们对使用热靶材提高材料的溅射沉积效果越来越感兴趣。然而，靶材表面的实际温度通常并不为人所知。在这项工作中，我们使用 K 型热电偶直接测量了 MAK 2 英寸钛水冷靶表面温度的径向分布。在溅射系统运行期间，我们使用 K 型热电偶直接测量了 MAK 2 英寸钛水冷靶表面温度的径向分布。测量结果主要是应用直流电功率和氩气压力的函数。鉴于反应溅射过程中气体和靶材之间化学反应的重要性，我们还测量了靶材温度与氩氮混合气体中氮气浓度的函数关系。我们用 X 射线光电子能谱分析了一些反应溅射样品。
{"title":"Surface temperature of a 2 in. Ti target during DC magnetron sputtering","authors":"Carlos Ramos, Daniela S. Jacobo-Mora, J. Cruz, Stephen Muhl","doi":"10.1116/6.0003481","DOIUrl":"https://doi.org/10.1116/6.0003481","url":null,"abstract":"Recently, there has been increasing interest in the use of hot targets to enhance the sputter deposition of materials. However, the actual temperature of the target surface is normally not known. In this work, we directly measured the radial distribution of the surface temperature of a MAK 2 in. Ti water-cooled target using a type K thermocouple during the operation of the sputtering system. Principally, the measurements were made as a function of applied DC power and argon gas pressure. Given the importance of chemical reactions between the gas and the target during reactive sputtering, we have also measured the target temperature as a function of the nitrogen concentration in an argon-nitrogen gas mixture. A few of the reactively sputtered samples were analyzed by x-ray photoelectron spectroscopy.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":" 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140217538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study utilized one-dimensional implicit particle-in-cell/Monte Carlo collision simulations to investigate the impact of different harmonic numbers and magnetic field strengths on capacitive-coupled argon plasma. Under the conditions of a pressure of 50 mTorr and a voltage of 100 V, simulations were conducted for magnetic field strengths of 0 and 100 G, magnetic field gradients of 10–40, 10–60, 10–80, 10–100, and 100–10 G, as well as discharge scenarios with harmonic numbers ranging from 1 to 5. Through in-depth analysis of the results, it was observed that the combined effect of positive magnetic field gradients and harmonic numbers can significantly enhance plasma density and self-bias properties to a greater extent. As the magnetic field gradient increases, the combined effect also increases, while an increase in harmonic numbers weakens the combined effect. Furthermore, this combined effect expands the range of control over ion bombardment energy. This provides a new research direction for improving control over ion energy and ion flux in capacitive-coupled plasmas.
{"title":"Effects of magnetic field gradient on capacitively coupled plasma driven by tailored voltage waveforms","authors":"Huanhuan Wu, Minghan Yan, Hao Wu, Shali Yang","doi":"10.1116/6.0003324","DOIUrl":"https://doi.org/10.1116/6.0003324","url":null,"abstract":"This study utilized one-dimensional implicit particle-in-cell/Monte Carlo collision simulations to investigate the impact of different harmonic numbers and magnetic field strengths on capacitive-coupled argon plasma. Under the conditions of a pressure of 50 mTorr and a voltage of 100 V, simulations were conducted for magnetic field strengths of 0 and 100 G, magnetic field gradients of 10–40, 10–60, 10–80, 10–100, and 100–10 G, as well as discharge scenarios with harmonic numbers ranging from 1 to 5. Through in-depth analysis of the results, it was observed that the combined effect of positive magnetic field gradients and harmonic numbers can significantly enhance plasma density and self-bias properties to a greater extent. As the magnetic field gradient increases, the combined effect also increases, while an increase in harmonic numbers weakens the combined effect. Furthermore, this combined effect expands the range of control over ion bombardment energy. This provides a new research direction for improving control over ion energy and ion flux in capacitive-coupled plasmas.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":" 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140216985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. A. A. Abdallah, R. Kroon, E. Coetsee, E. Hasabeldaim, H. Swart
Eu3+ ion doped CaF2 thin film was successfully prepared using the hydrothermal method and coated by a spin coating technique. A thin layer of ZnO was deposited on the Eu3+ doped CaF2 thin film by pulsed laser technique. Incorporation of the dopant into the CaF2 crystal was confirmed by x-ray powder diffraction and x-ray photoelectron spectroscopy (XPS). Excitation of the film at 227 nm produced the characteristic emissions of Eu3+ ions. The stability of the film under electron beam bombard was studied using Auger electron spectroscopy, cathodoluminescence (CL), and XPS. The CL and Auger peak-to-peak heights (APPHs) data were collected concurrently using the same electron beam. The APPH of Ca and O increased, while that of F decreased, which indicated the conversion of CaF2 to CaO. The CL emission decreased initially during degradation and stabilized beyond 48 C/cm2 for the film with the ZnO coating. XPS analysis also indicated the dissociation of the fluoride compounds and subsequent formation of oxide compounds such as CaO and EuO after electron beam degradation.
{"title":"Stability investigation of Eu3+ doped CaF2 thin film with ZnO coating under electron beam irradiation","authors":"R. A. A. Abdallah, R. Kroon, E. Coetsee, E. Hasabeldaim, H. Swart","doi":"10.1116/6.0003363","DOIUrl":"https://doi.org/10.1116/6.0003363","url":null,"abstract":"Eu3+ ion doped CaF2 thin film was successfully prepared using the hydrothermal method and coated by a spin coating technique. A thin layer of ZnO was deposited on the Eu3+ doped CaF2 thin film by pulsed laser technique. Incorporation of the dopant into the CaF2 crystal was confirmed by x-ray powder diffraction and x-ray photoelectron spectroscopy (XPS). Excitation of the film at 227 nm produced the characteristic emissions of Eu3+ ions. The stability of the film under electron beam bombard was studied using Auger electron spectroscopy, cathodoluminescence (CL), and XPS. The CL and Auger peak-to-peak heights (APPHs) data were collected concurrently using the same electron beam. The APPH of Ca and O increased, while that of F decreased, which indicated the conversion of CaF2 to CaO. The CL emission decreased initially during degradation and stabilized beyond 48 C/cm2 for the film with the ZnO coating. XPS analysis also indicated the dissociation of the fluoride compounds and subsequent formation of oxide compounds such as CaO and EuO after electron beam degradation.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":" 30","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140221613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Luchechko, V. Vasyltsiv, M. Kushlyk, L. Kostyk, D. Slobodzyan
Photoluminescence, luminescence excitation spectra, and electrical conductivity of β-Ga2O3-In2O3 solid solutions were studied. For this purpose, polycrystalline samples of unintentionally doped (UID) and doped with Ca or Zr β-Ga2O3-In2O3 solid solution with 20% In were synthesized and characterized. All samples were obtained by the high-temperature solid-phase method from appropriate oxides at 1300 °C at low and high oxygen partial pressure. It was established that UID and doped with Ca2+ or Zr4+ samples synthesized in an oxygen atmosphere were highly resistive, while the samples synthesized in an argon atmosphere had high conductivity. The conductivity was the lowest in the samples doped with Ca2+ and was 10−13 Ω−1 cm−1, while in the samples doped with Zr4+, the electrical conductivity was the highest and reached 10−3 Ω−1 cm−1. The broadband luminescence of β-Ga2O3-In2O3 solid solution is a superposition of three elementary bands with maxima in the violet 3.08 eV, blue 2.73 eV, and green 2.45 eV regions of the spectrum. Doping with Ca2+ or Zr4+ impurities and varying the synthesis atmosphere led mainly to a redistribution of intensities between the elementary luminescence bands. The luminescence arises from the radiative recombination of charge carriers through donor–acceptor pairs and self-localized holes. Donors and acceptors are formed by native defects such as (Gai, VGa, VGaVo) or doping impurities (Zr4+, Ca2+). Unlike the luminescence spectra, the luminescence excitation spectra change significantly when the synthesis conditions vary or when doping with divalent impurities. The excitation band at 4.46 eV is due to electron transitions from the VGa or VGaVO acceptor levels to the conduction band. Electron transitions from acceptor levels of Ca2+ impurities are manifested in the intense excitation band at 4.1 eV.
研究了β-Ga2O3-In2O3 固溶体的光致发光、发光激发光谱和导电性。为此，合成并表征了无意掺杂（UID）和含 20% In 的掺 Ca 或 Zr β-Ga2O3-In2O3 固溶体的多晶样品。所有样品都是通过高温固相法在 1300 ℃、低氧分压和高氧分压下从适当的氧化物中获得的。结果表明，在氧气氛中合成的 UID 和掺有 Ca2+ 或 Zr4+ 的样品电阻率很高，而在氩气氛中合成的样品电导率很高。掺杂 Ca2+ 的样品导电率最低，为 10-13 Ω-1 cm-1，而掺杂 Zr4+ 的样品导电率最高，达到 10-3 Ω-1 cm-1。β-Ga2O3-In2O3 固溶体的宽带发光是三个基本波段的叠加，最大值分别位于光谱的紫色 3.08 eV、蓝色 2.73 eV 和绿色 2.45 eV 区域。掺入 Ca2+ 或 Zr4+ 杂质以及改变合成气氛主要导致基本发光带之间强度的重新分配。发光源于电荷载流子通过供体-受体对和自定位空穴的辐射重组。供体和受体由原生缺陷（Gai、VGa、VGaVo）或掺杂杂质（Zr4+、Ca2+）形成。与发光光谱不同，当合成条件发生变化或掺入二价杂质时，发光激发光谱会发生显著变化。4.46 eV 处的激发带是由于电子从 VGa 或 VGaVO 受体水平跃迁到导带所致。来自 Ca2+ 杂质受主级的电子跃迁表现为 4.1 eV 处的强激发带。
{"title":"Electrical conductivity, luminescence, and deep acceptor levels in β-Ga2O3-In2O3 polycrystalline solid solution doped with Zr4+ or Ca2+ ions","authors":"A. Luchechko, V. Vasyltsiv, M. Kushlyk, L. Kostyk, D. Slobodzyan","doi":"10.1116/6.0003466","DOIUrl":"https://doi.org/10.1116/6.0003466","url":null,"abstract":"Photoluminescence, luminescence excitation spectra, and electrical conductivity of β-Ga2O3-In2O3 solid solutions were studied. For this purpose, polycrystalline samples of unintentionally doped (UID) and doped with Ca or Zr β-Ga2O3-In2O3 solid solution with 20% In were synthesized and characterized. All samples were obtained by the high-temperature solid-phase method from appropriate oxides at 1300 °C at low and high oxygen partial pressure. It was established that UID and doped with Ca2+ or Zr4+ samples synthesized in an oxygen atmosphere were highly resistive, while the samples synthesized in an argon atmosphere had high conductivity. The conductivity was the lowest in the samples doped with Ca2+ and was 10−13 Ω−1 cm−1, while in the samples doped with Zr4+, the electrical conductivity was the highest and reached 10−3 Ω−1 cm−1. The broadband luminescence of β-Ga2O3-In2O3 solid solution is a superposition of three elementary bands with maxima in the violet 3.08 eV, blue 2.73 eV, and green 2.45 eV regions of the spectrum. Doping with Ca2+ or Zr4+ impurities and varying the synthesis atmosphere led mainly to a redistribution of intensities between the elementary luminescence bands. The luminescence arises from the radiative recombination of charge carriers through donor–acceptor pairs and self-localized holes. Donors and acceptors are formed by native defects such as (Gai, VGa, VGaVo) or doping impurities (Zr4+, Ca2+). Unlike the luminescence spectra, the luminescence excitation spectra change significantly when the synthesis conditions vary or when doping with divalent impurities. The excitation band at 4.46 eV is due to electron transitions from the VGa or VGaVO acceptor levels to the conduction band. Electron transitions from acceptor levels of Ca2+ impurities are manifested in the intense excitation band at 4.1 eV.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"70 s1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140225241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ai Iwai, S. Aonuki, Shunsuke Narita, Kaori Takayanagi, K. Toko, T. Suemasu
We evaluated the effect of O atoms on the postannealed BaSi2 films grown by molecular beam epitaxy. Postannealing (PA) in an Ar atmosphere at a pressure of 1.9 × 105 Pa increased the O concentration to 7 × 1020 cm−3 in the bulk region and further increased to ∼1022 cm−3 at the BaSi2/Si interface. Cracks formed during the PA process, allowing O to enter more easily to the BaSi2 films. In the x-ray photoelectron spectroscopy spectrum of the Si 2s core level measured at 10 nm from the surface, a shift of the peak related to SiOx was detected, indicating a change in the bonding state of Si and O in this region. When PA was performed in vacuum at 10−3 Pa, the photoresponsivity in the short wavelength region was enhanced, with a maximum value of 6.6 A W−1 at 790 nm. The O concentration in the film decreased in the sample annealed in vacuum, and the PL peak intensity at 0.85 eV decreased, suggesting that this was due to a decrease in O-related defects compared to the Ar atmosphere. However, agglomeration of BaSi2 caused significant surface roughness, indicating the importance of PA conditions that minimize O uptake and keep the surface smooth for improved performance of BaSi2 solar cells.
我们评估了 O 原子对分子束外延生长的退火后 BaSi2 薄膜的影响。在压力为 1.9 × 105 Pa 的氩气环境中进行的后退火（PA）使块状区域的 O 浓度增加到 7 × 1020 cm-3，并在 BaSi2/Si 界面进一步增加到 ∼1022 cm-3。在 PA 过程中形成了裂缝，使 O 更容易进入 BaSi2 薄膜。在距离表面 10 nm 处测量的 Si 2s 核心水平的 X 射线光电子能谱中，检测到与 SiOx 有关的峰值发生了移动，这表明该区域中 Si 和 O 的成键状态发生了变化。在 10-3 Pa 的真空中进行 PA 时，短波长区域的光致发光率得到增强，在 790 nm 波长处的最大值为 6.6 A W-1。在真空中退火的样品中，薄膜中的 O 浓度降低，0.85 eV 处的 PL 峰强度降低，这表明与 Ar 气氛相比，与 O 有关的缺陷减少了。然而，BaSi2 的团聚造成了明显的表面粗糙，这表明 PA 条件对提高 BaSi2 太阳能电池性能的重要性，PA 条件应能最大限度地减少 O 的吸收并保持表面光滑。
{"title":"Effect of high-temperature postannealing atmosphere on the properties of BaSi2 films","authors":"Ai Iwai, S. Aonuki, Shunsuke Narita, Kaori Takayanagi, K. Toko, T. Suemasu","doi":"10.1116/6.0003505","DOIUrl":"https://doi.org/10.1116/6.0003505","url":null,"abstract":"We evaluated the effect of O atoms on the postannealed BaSi2 films grown by molecular beam epitaxy. Postannealing (PA) in an Ar atmosphere at a pressure of 1.9 × 105 Pa increased the O concentration to 7 × 1020 cm−3 in the bulk region and further increased to ∼1022 cm−3 at the BaSi2/Si interface. Cracks formed during the PA process, allowing O to enter more easily to the BaSi2 films. In the x-ray photoelectron spectroscopy spectrum of the Si 2s core level measured at 10 nm from the surface, a shift of the peak related to SiOx was detected, indicating a change in the bonding state of Si and O in this region. When PA was performed in vacuum at 10−3 Pa, the photoresponsivity in the short wavelength region was enhanced, with a maximum value of 6.6 A W−1 at 790 nm. The O concentration in the film decreased in the sample annealed in vacuum, and the PL peak intensity at 0.85 eV decreased, suggesting that this was due to a decrease in O-related defects compared to the Ar atmosphere. However, agglomeration of BaSi2 caused significant surface roughness, indicating the importance of PA conditions that minimize O uptake and keep the surface smooth for improved performance of BaSi2 solar cells.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"10 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140226288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Perovskite CaIrO3 is theoretically predicted to be a Dirac node semimetal near the Mott transition, which possesses a considerable interplay between electron correlations and spin–orbit coupling. Electron correlations can significantly tune the behavior of relativistic Dirac fermions. Here, we have grown high-quality perovskite CaIrO3 thin films on different substrates using oxide molecular beam epitaxy to modulate both electron correlations and Dirac electron states. Through in situ angle-resolved photoemission spectroscopy, we demonstrate a systematic evolution of the bandwidth and effective mass of Jeff=1/2 band in perovskite CaIrO3 induced by strain. The bandwidth of the Jeff=1/2 band undergoes an evident increase under in-plane compressive strain, which could be attributed to the weakening of electron correlations. The compressive strain can potentially shift the position of the Dirac node relative to the Fermi level and play a vital role in the transition from hole-type to electron-type transport characteristics. Our work provides a feasible approach for manipulating the topological Dirac electron states by engineering the strength of electron correlations.
{"title":"Strain-induced modulation of electronic structure in correlated Dirac semimetal Pv-CaIrO3 epitaxial thin films","authors":"Jian-ming Ding, Zhengtai Liu, Jiayu Liu, Jian Yuan, Liyang Wei, Zhicheng Jiang, Yichen Yang, Chihao Li, Yilin Wang, Yanfeng Guo, Mao Ye, Jishan Liu, Dawei Shen","doi":"10.1116/6.0003462","DOIUrl":"https://doi.org/10.1116/6.0003462","url":null,"abstract":"Perovskite CaIrO3 is theoretically predicted to be a Dirac node semimetal near the Mott transition, which possesses a considerable interplay between electron correlations and spin–orbit coupling. Electron correlations can significantly tune the behavior of relativistic Dirac fermions. Here, we have grown high-quality perovskite CaIrO3 thin films on different substrates using oxide molecular beam epitaxy to modulate both electron correlations and Dirac electron states. Through in situ angle-resolved photoemission spectroscopy, we demonstrate a systematic evolution of the bandwidth and effective mass of Jeff=1/2 band in perovskite CaIrO3 induced by strain. The bandwidth of the Jeff=1/2 band undergoes an evident increase under in-plane compressive strain, which could be attributed to the weakening of electron correlations. The compressive strain can potentially shift the position of the Dirac node relative to the Fermi level and play a vital role in the transition from hole-type to electron-type transport characteristics. Our work provides a feasible approach for manipulating the topological Dirac electron states by engineering the strength of electron correlations.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"360 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140228078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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