We fabricated La_(1-x)Sr_xMnO_3/Si(LSMO/Si) heterojunctions with different Sr doping concentrations(x = 0.1, 0.2,0.3) in LSMO and studied the Sr content influence on magnetoresistance(MR) ratio.The hetero junctions show positive MR and high sensitivity of MR ratio in a low applied magnetic field.The MR ratio is dependent on Sr content and the low Sr doping in LSMO causes a large positive MR in LSMO/Si junctions.The MR ratio for 0.1 Sr doping in the LSMO/Si heterostructure is 116%in 100 Oe(1 Oe=79.5775 A/m) at 210 K.The mechanism for the positive MR dependence on the doping density is considered to be the competition between the tunneling rate of electrons in e_g^1↑to t_(2g)↓band and that to e_g^2↑band at the interface region of LSMO.The experimental results are in agreement with those observed in La_(0.9)Sr_(0.1)MnO_3/SrNb_(0.01)Ti_(0.99)O_3 p-n junction.The results indicate that choosing low doping concentration to improve the low field sensitivity of the heterojunction devices is a very efficacious method.
A field-effect configuration based on La0.9Sr0.1MnO3/SrTiO3/Si structure is fabricated on Si substrate by laser molecular-beam epitaxy. The resistance modulation by electric field of the La0.9Sr0.1MnO3/SrTiO3/Si structure is investigated in detail. An evident resistance modulation effect is observed at 80 K. The channel resistance modulation by field effect reaches 1.4×107% and 2.6×106% when VDS are -2 and -6.5 V, respectively. The ON/OFF ratio of approximately 4000 is obtained. The present results are worthy of further investigations for potential applications of resistance modulation by electrostatic field in the heterostructures consisting of perovskite oxides and Si.
YANG Fang, HE Meng, WEN Juan, JIN KuiJuan, LU HuiBin & YANG GuoZhen Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
The unusual magnetic properties are observed in oxygen deficient BaTiO3-δ(BTO) and Nb:BaTiO3-δ(BNTO) thin films fabricated on SrTiO3 substrates by laser molecular beam epitaxy.The distinct magnetic hysteresis loops are observed in the oxygen deficient BTO and BNTO thin films in a temperature range of 5 to 300 K,whereas the diamagnetism is observed in both BTO and BNTO annealed at 1 atm of oxygen.The dopant Nb only enhances the magnetization in BNTO thin films,but has little effect on the coercivity.The magnetism of BTO and BNTO films is proposed to be the oxygen vacancies by origin.
YANG Fang,JIN KuiJuan,LU HuiBin,HE Meng,WANG Cong,WEN Juan & YANG GuoZhen Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China
A high sensitivity photovoltaic effect has been observed in a heterojunction composed of n-type wide bandgap oxide SrTiO 3-δ and p-type Si fabricated by laser molecular beam epitaxy.The responsivity of open-circuit photovoltage can reach 10 4 V/W without any amplification under zero bias for the wavelength range from visible to near infrared light in nW-μW order.We attribute the high performance of the photovoltage responsivity to the interfacial photoelectric effects in the SrTiO 3-δ /Si heterojunction.From the experimental results,some ideas can be generalized to improve photovoltaic efficiency and develop high sensitivity photodetectors with wide bandgap oxide materials and Si.
WEN Juan 1,GUO HaiZhong 1,XING Jie 2,Lü HuiBin 1,JIN Kui-Juan 1,HE Meng 1 & YANG GuoZhen 1 1 Beijing National Laboratory for Condensed Matter Physics,Institute of Physics,Chinese Academy of Sciences,Beijing 100190,China
