ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by ... more ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by doping with oxygen vacancies induced by Ar+ ion irradiation. The conducting channels exhibit a consistently high electron mobility (~15,000 cm2 V−1 s−1), which enables a clear observation of magnetic quantum oscillations, and a gate-tunable linear magnetoresistance. Near the onset of electrical conduction, a metal-insulator transition is induced by mobility suppression. With the high electron mobility and the ease of controlled channel formation, this ion irradiation doping method may provide an excellent basis for developing oxide electronics.
We report the fabrication and electrical measurements for LaAlO 3 /SrTiO 3 (LAO/STO) heterostruct... more We report the fabrication and electrical measurements for LaAlO 3 /SrTiO 3 (LAO/STO) heterostructures having various lateral sizes. When the sample size is reduced to the sub-micrometer range, the magnetoconductance (MC) curve deviates from classical parabolic behavior. Instead, a negative MC behavior appears with superimposed conductance fluctuations, which is attributed to weak antilocalization and universal conductance fluctuations. Using the Maekawa-Fukuyama model, the spin-orbit scattering and phase coherence lengths are estimated from the MC data, which are dependent on the gate voltage and temperature. Our comprehensive study shows that LAO/STO heterointerfaces provide a useful platform to explore quantum coherent transport of strongly correlated electrons. #
ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by ... more ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by doping with oxygen vacancies induced by Ar+ ion irradiation. The conducting channels exhibit a consistently high electron mobility (~15,000 cm2 V−1 s−1), which enables a clear observation of magnetic quantum oscillations, and a gate-tunable linear magnetoresistance. Near the onset of electrical conduction, a metal-insulator transition is induced by mobility suppression. With the high electron mobility and the ease of controlled channel formation, this ion irradiation doping method may provide an excellent basis for developing oxide electronics.
We have observed the zero-crossing steps in a surface junction of a mesa structure micro-fabricat... more We have observed the zero-crossing steps in a surface junction of a mesa structure micro-fabricated on the surface of a Bi 2 Sr 2 CaCu 2 O 8+δ single crystal. With the application of microwave of frequencies 76 and 94 GHz, the currentvoltage characteristics show clear voltage steps satisfying the ac Josephson relation. Increasing the microwave power, the heights of the steps show the Bessel-function behavior up to step number n = 4. We confirm that the intrinsic surface junction meets the criterion for the observation of zero-crossing steps.
Stacks of a few intrinsic tunnel junctions were micro-fabricated on the surface of Bi 2 Sr 2 CaCu... more Stacks of a few intrinsic tunnel junctions were micro-fabricated on the surface of Bi 2 Sr 2 CaCu 2 O 8+δ single crystals. The number of junctions in a stack was tailored by progressively increasing the height of the stack by ion-beam etching, while its tunneling characteristics were measured in-situ in a vacuum chamber for temperatures down to ∼13 K. Using this in-situ etching/measurements technique in a single piece of crystal, we systematically excluded any spurious effects arising from variations in the junction parameters and made clear analysis on the following properties of the surface and inner conducting planes. First, the tunneling resistance and the current-voltage curves are scaled by the surface junction resistance. Second, we confirm that the reduction in both the gap and the superconducting transition temperature of the surface conducting plane in contact with a normal metal is not caused by the variation in the doping level, but is caused by the proximity contact.
The microwave response of small stacks of intrinsic Josephson junctions in HgI2-intercalated Bi2S... more The microwave response of small stacks of intrinsic Josephson junctions in HgI2-intercalated Bi2Sr2CaCu2O8 single crystals was studied. When irradiated with a microwave of frequencies higher than the junction plasma frequency, the supercurrent branch becomes resistive ...
We have studied the ac Josephson effect using an intrinsic Josephson junction fabricated on the s... more We have studied the ac Josephson effect using an intrinsic Josephson junction fabricated on the surface of Bi2Sr2CaCu2Os+6 single crystals. Irradiated with external microwave of f = 76 and 94 GHz, the I-V characteristics show clear constant-voltage steps crossing the zero-current line. These steps satisfy the ac Josephson relation and the step heights show the Bessel-function behavior with increasing microwave power, corresponding to step numbers up to n = 4. The intrinsic surface junction with a very low critical current density meets the criterion for observing zero-crossing steps.
ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by ... more ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by doping with oxygen vacancies induced by Ar+ ion irradiation. The conducting channels exhibit a consistently high electron mobility (~15,000 cm2 V−1 s−1), which enables a clear observation of magnetic quantum oscillations, and a gate-tunable linear magnetoresistance. Near the onset of electrical conduction, a metal-insulator transition is induced by mobility suppression. With the high electron mobility and the ease of controlled channel formation, this ion irradiation doping method may provide an excellent basis for developing oxide electronics.
We report the fabrication and electrical measurements for LaAlO 3 /SrTiO 3 (LAO/STO) heterostruct... more We report the fabrication and electrical measurements for LaAlO 3 /SrTiO 3 (LAO/STO) heterostructures having various lateral sizes. When the sample size is reduced to the sub-micrometer range, the magnetoconductance (MC) curve deviates from classical parabolic behavior. Instead, a negative MC behavior appears with superimposed conductance fluctuations, which is attributed to weak antilocalization and universal conductance fluctuations. Using the Maekawa-Fukuyama model, the spin-orbit scattering and phase coherence lengths are estimated from the MC data, which are dependent on the gate voltage and temperature. Our comprehensive study shows that LAO/STO heterointerfaces provide a useful platform to explore quantum coherent transport of strongly correlated electrons. #
ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by ... more ABSTRACT We report on the controlled formation of sub-100-nm-thin electron channels in SrTiO3 by doping with oxygen vacancies induced by Ar+ ion irradiation. The conducting channels exhibit a consistently high electron mobility (~15,000 cm2 V−1 s−1), which enables a clear observation of magnetic quantum oscillations, and a gate-tunable linear magnetoresistance. Near the onset of electrical conduction, a metal-insulator transition is induced by mobility suppression. With the high electron mobility and the ease of controlled channel formation, this ion irradiation doping method may provide an excellent basis for developing oxide electronics.
We have observed the zero-crossing steps in a surface junction of a mesa structure micro-fabricat... more We have observed the zero-crossing steps in a surface junction of a mesa structure micro-fabricated on the surface of a Bi 2 Sr 2 CaCu 2 O 8+δ single crystal. With the application of microwave of frequencies 76 and 94 GHz, the currentvoltage characteristics show clear voltage steps satisfying the ac Josephson relation. Increasing the microwave power, the heights of the steps show the Bessel-function behavior up to step number n = 4. We confirm that the intrinsic surface junction meets the criterion for the observation of zero-crossing steps.
Stacks of a few intrinsic tunnel junctions were micro-fabricated on the surface of Bi 2 Sr 2 CaCu... more Stacks of a few intrinsic tunnel junctions were micro-fabricated on the surface of Bi 2 Sr 2 CaCu 2 O 8+δ single crystals. The number of junctions in a stack was tailored by progressively increasing the height of the stack by ion-beam etching, while its tunneling characteristics were measured in-situ in a vacuum chamber for temperatures down to ∼13 K. Using this in-situ etching/measurements technique in a single piece of crystal, we systematically excluded any spurious effects arising from variations in the junction parameters and made clear analysis on the following properties of the surface and inner conducting planes. First, the tunneling resistance and the current-voltage curves are scaled by the surface junction resistance. Second, we confirm that the reduction in both the gap and the superconducting transition temperature of the surface conducting plane in contact with a normal metal is not caused by the variation in the doping level, but is caused by the proximity contact.
The microwave response of small stacks of intrinsic Josephson junctions in HgI2-intercalated Bi2S... more The microwave response of small stacks of intrinsic Josephson junctions in HgI2-intercalated Bi2Sr2CaCu2O8 single crystals was studied. When irradiated with a microwave of frequencies higher than the junction plasma frequency, the supercurrent branch becomes resistive ...
We have studied the ac Josephson effect using an intrinsic Josephson junction fabricated on the s... more We have studied the ac Josephson effect using an intrinsic Josephson junction fabricated on the surface of Bi2Sr2CaCu2Os+6 single crystals. Irradiated with external microwave of f = 76 and 94 GHz, the I-V characteristics show clear constant-voltage steps crossing the zero-current line. These steps satisfy the ac Josephson relation and the step heights show the Bessel-function behavior with increasing microwave power, corresponding to step numbers up to n = 4. The intrinsic surface junction with a very low critical current density meets the criterion for observing zero-crossing steps.
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Papers by Yong-Joo Doh