Electrical field and light-illumination have been two most widely used stimuli in tuning the conductivity of semiconductor devices. Via capacitive effect electrical field modifies the carrier density of the devices, while light-illumination generates
extra carriers by exciting trapped electrons into conduction band1. Here, we report on an unexpected light illumination enhanced field effect in a quasi-two-dimensional electron gas (q2DEG) confined at the LaAlO3/SrTiO3 (LAO/STO) interface which has been the focus of emergent phenomenon exploration2-14. We found that light illumination greatly accelerates and amplifies the field effect, driving the field-induced resistance growth which originally lasts for thousands of seconds into an abrupt resistance jump more than two orders of magnitude. Also, the field-induced change in carrier density is much larger than that expected from the capacitive effect, and can even be opposite to the conventional photoelectric effect. This work expands the space for novel effect exploration and multifunctional device design at complex oxide interfaces.
Carrier injection performed in oxygen-deficient YBa2Cu3O7(YBCO) hetero-structure junctions exhibited tunable resistance that was entirely different with behaviors of semiconductor devices. Tunable superconductivity in YBCO junctions, increasing over
20 K in transition temperature, has achieved by using electric processes. To our knowledge, this is the first observation that intrinsic property of high TC superconductors superconductivity can be adjusted as tunable functional parameters of devices. The fantastic phenomenon caused by carrier injection was discussed based on a proposed charge carrier self-trapping model and BCS theory.
In doped manganites, the strong electron-phonon coupling due to the Jahn-Teller effect localizes the conduction-band electrons as polarons. This results in polarons are carriers responsible for transport and ferromagnetic ordering rather than the bar
e eg electrons, and sequentially polaron exchange model is emerged for describing ferromagnetic ordering. In Pr0.7(Sr1-xCax)0.3MnO3(x=0.3-0.6) epitaxial thin films, for higher-temperature paramagnetic state and lower-temperature ferromagnetic state, both the temperature dependent transports present behaviors of small polaron; for paramagnetic-ferromagnetic transition, the experimental data of Curie temperature are well described by an energy balance expression induced by polaron exchange model. These results demonstrate that the polaron models are proper ways to describe the strongly correlated electrons in the doped manganites.
Charge carrier injection performed in Pr0.7Ca0.3MnO3 (PCMO) hetero-structure junctions exhibits stable without electric fields and dramatic changes in both resistances and interface barriers, which are entirely different from behaviors of semiconduct
or devices. Disappearance and reversion of interface barriers suggest that the adjustable resistance switching of such hetero-structure oxide devices should associate with motion of charge carriers across interfaces. The results suggested that injected carriers should be still staying in devices and resulted in changes in properties, which guided to a carrier self-trapping and releasing picture in strongly correlated electronic framework. Observations in PCMO and oxygen deficient CeO2 devices show that oxides as functional materials could be used in microelectronics with some novel properties, in which interface is very important.
