摘要
采用脉冲激光沉积(PLD)技术,在0~15°斜切的α-Al_(2)O_(3)(0001)衬底上生长了c轴外延的CuCr_(1-x)Mg_(x)O_(2)(x=0-0.08)系列薄膜。随Mg掺杂量增加,薄膜均为单相铜铁矿结构,表现出符合Arrhenius热激活模式的半导体电输运行为,室温电阻率单调下降2~3个数量级,热激活能由0.22 eV下降至0.025 eV,由此推断薄膜中Mg的固溶度至少为0.08,与多晶(~0.03)相比显著扩展。这是由于PLD薄膜生长具有非平衡、瞬时爆炸特征,使靶材第二相(MgCr_(2)O_(4))中的Mg重新以等离子态定向运输到衬底上,迁移固溶到薄膜晶格中,固溶度扩展。薄膜(x=0,0.02)在380~780 nm可见光区的透过率为60%~80%,直接光学带隙E g分别为3.06 eV、3.04 eV。更多Mg^(2+)替代Cr^(3+)时,会在价带顶上方引入受主能级并展宽,使热激活能显著下降,产生更多空穴载流子,透过率和光学带隙略有下降;Mg固溶到晶格中,促进薄膜层状晶粒长大,外延性提高,使电阻率进一步下降。
The c-axis epitaxial CuCr_(1-x)Mg_(x)O_(2)(x=0-0.08) thin films were grown on the 0—15°vicinal cutα-Al_(2)O_(3)(0001)substrate by pulsed laser deposition(PLD)technology.With the increase of Mg doping,the thin films are all single-phase delafossite structure.The thin films exhibit semiconductor behavior,which conforms to Arrhenius thermal activation mode.The room temperature resistivity decreased monotonically by 2—3 orders of magnitude,the thermal activation energy dropped from 0.22 eV to 0.025 eV.It was inferred that the solid solubility of Mg in the thin film was at least 0.08,which was significantly extended compared with polycrystalline(~0.03).The non-equilibrium and instantaneous explosion characteristics of PLD make Mg in the target second phase(MgCr_(2)O_(4))transport to the substrate by plasma,and dissolve into the thin film lattice,resulting in an extension of the solid solubility.The transmittance of the thin films(x=0,0.02)was 60%—80%in the visible light region of 380—780 nm.The direct optical bandgap E g was 3.06 eV,3.04 eV,respectively.The acceptor energy level is introduced and broadened above the valence band top while more Cr^(3+) replaced by Mg^(2+),making thermal activation energy decrease significantly,the more carriers can be gene-rated.The transmittance and optical band gap have a slight drop.When Mg is solid-dissolved into the crystal lattice,which promotes the growth of layered crystal grains of the thin films,the epitaxialitye are improved,and the resistivity is further reduced.
作者
沈艳
刘丹丹
宋世金
唐艳艳
胡一丁
武浩荣
虞澜
SHEN Yan;LIU Dandan;SONG Shijin;TAN Yanyan;HU Yiding;WU Haorong;YU Lan(Faculty of Materials Science and Engineering,Kunming University of Science and Technology,Kunming 650093,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2021年第10期10008-10012,共5页
Materials Reports
基金
国家自然科学基金(51962017,51462017)。
作者简介
沈艳,昆明理工大学材料学硕士研究生,主要研究方向为光电子材料与器件;虞澜,昆明理工大学材料学院教授,博士研究生导师。2012年6月获得昆明理工大学与德国马普固体研究所联合培养的材料学专业博士学位。主要从事强关联体系和原子层热电堆特征氧化物、半导体热(光)电材料的多晶陶瓷和外延薄膜的制备表征、热电磁输运各向异性、横向热电效应,以及原子层热电堆薄膜热流传感器研发。在国内外学术期刊上发表论文50余篇,申请发明专利25项,其中授权11项,yulan000@hotmail. com。
