M. Gonzalez, A. Ievlev, K. Lee, W. Kim, Y. Yu, J. Fowlie, H. Y. Hwang
{"title":"Absence of hydrogen insertion into highly crystalline superconducting infinite layer nickelates","authors":"M. Gonzalez, A. Ievlev, K. Lee, W. Kim, Y. Yu, J. Fowlie, H. Y. Hwang","doi":"10.1103/physrevmaterials.8.084804","DOIUrl":null,"url":null,"abstract":"The discovery of superconductivity in the infinite layer nickelates introduced a materials system analogous to the cuprates for the study of unconventional superconductivity. The synthesis of infinite layer nickelates, (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>RNiO</mi><mn>2</mn></msub></math>, R = lanthanide) often uses calcium hydride (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>CaH</mi><mn>2</mn></msub></math>) to facilitate the deintercalation of apical site oxygen atoms from a precursor perovskite (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>RNiO</mi><mn>3</mn></msub></math>) phase via topotactic reduction. However, it remains uncertain whether the use of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>CaH</mi><mn>2</mn></msub></math> results in the insertion of hydrogen into the infinite layer structure, and if it does, what the implications are for superconductivity. To quantify the hydrogen composition of highly crystalline infinite layer nickelates, we synthesized <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Nd</mi><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub><msub><mi>Sr</mi><mi>x</mi></msub><msub><mi>NiO</mi><mn>2</mn></msub></mrow></math> thin films on LSAT substrates and conducted time-of-flight secondary ion mass spectroscopy measurements to generate hydrogen depth profiles. We compare the hydrogen density of nickelates prepared with and without a <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>SrTiO</mi><mn>3</mn></msub></math> capping layer. Additionally, we measure the hydrogen content in nickelate samples at various doping levels spanning the superconducting phase space, including the underdoped, optimally doped, and overdoped regime. We report no significant increase in hydrogen density between the perovskite and infinite layer phases in any of the measured samples. Furthermore, we put an upperbound on the hydrogen concentration of our nickelate samples to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Nd</mi><mrow><mn>1</mn><mo>−</mo><mi>x</mi></mrow></msub><msub><mi>Sr</mi><mi>x</mi></msub><msub><mi>NiO</mi><mn>2</mn></msub><msub><mi mathvariant=\"normal\">H</mi><mrow><mn>0.05</mn></mrow></msub></mrow></math>. Our results imply that hydrogen is not responsible for the emergence of superconductivity in the infinite layer nickelates.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"4 1","pages":""},"PeriodicalIF":3.1000,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physical Review Materials","FirstCategoryId":"88","ListUrlMain":"https://doi.org/10.1103/physrevmaterials.8.084804","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The discovery of superconductivity in the infinite layer nickelates introduced a materials system analogous to the cuprates for the study of unconventional superconductivity. The synthesis of infinite layer nickelates, (, R = lanthanide) often uses calcium hydride () to facilitate the deintercalation of apical site oxygen atoms from a precursor perovskite () phase via topotactic reduction. However, it remains uncertain whether the use of results in the insertion of hydrogen into the infinite layer structure, and if it does, what the implications are for superconductivity. To quantify the hydrogen composition of highly crystalline infinite layer nickelates, we synthesized thin films on LSAT substrates and conducted time-of-flight secondary ion mass spectroscopy measurements to generate hydrogen depth profiles. We compare the hydrogen density of nickelates prepared with and without a capping layer. Additionally, we measure the hydrogen content in nickelate samples at various doping levels spanning the superconducting phase space, including the underdoped, optimally doped, and overdoped regime. We report no significant increase in hydrogen density between the perovskite and infinite layer phases in any of the measured samples. Furthermore, we put an upperbound on the hydrogen concentration of our nickelate samples to . Our results imply that hydrogen is not responsible for the emergence of superconductivity in the infinite layer nickelates.
期刊介绍:
Physical Review Materials is a new broad-scope international journal for the multidisciplinary community engaged in research on materials. It is intended to fill a gap in the family of existing Physical Review journals that publish materials research. This field has grown rapidly in recent years and is increasingly being carried out in a way that transcends conventional subject boundaries. The journal was created to provide a common publication and reference source to the expanding community of physicists, materials scientists, chemists, engineers, and researchers in related disciplines that carry out high-quality original research in materials. It will share the same commitment to the high quality expected of all APS publications.