Ruijia Liu

Bio: Ruijia Liu is an academic researcher from Pennsylvania State University. The author has contributed to research in topics: Materials science & Ferroelectricity. The author has an hindex of 4, co-authored 11 publications receiving 46 citations. Previous affiliations of Ruijia Liu include Chongqing University.

Enhanced electro-optic beam deflection of relaxor ferroelectric KTN crystals by electric-field-induced high permittivity

Abstract: Most applications of a ferroelectric-based electro-optic (EO) beam deflector have been limited by the high applied voltage. In this Letter, we report a dramatically increased EO beam deflection in relaxor ferroelectric potassium tantalate niobate (KTN) crystals by using the electric-field-enhanced permittivity. Due to the existence of the electric-field-induced phase transition in relaxor ferroelectric materials, the dielectric permittivity can be substantially increased by the applied electric field at a certain temperature. Both the theoretical study and the experimental verifications on the enhanced beam deflection and EO effect in the case with the electric-field-induced high permittivity were conducted. The experimental results confirmed that there was a three-fold increase in the deflection angle, which represented a dramatic increase in the deflection angle. By offering a wider deflection range and a lower driving voltage, such a largely enhanced beam deflection is of great benefit to the KTN deflector.

SERS and the photo-catalytic performance of Ag/TiO2/graphene composites

Abstract: Three kinds of reusable surface enhanced Raman scattering (SERS) substrates based on Ag-TiO2-G, Ag-G-TiO2 and G-Ag-TiO2 hybrid structures were prepared by a combination method of simple sol-gel self-assembly and annealing. The composites were confirmed by transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Raman mapping spectra of the three hybrids were analyzed in order to study the difference of charge transfer between Ag, TiO2 and graphene. In addition, rhodamine 6G (R6G) was used as the probe analyte, and the SERS activity of the three structures decreased orderly in the sequence of Ag-G-TiO2, G-Ag-TiO2, and Ag-TiO2-G, with the enhancement factor of about 106, which was due to the high electromagnetic enhancement of the Ag nanoparticles (AgNPs). The photo-catalytic properties of the three kinds of composites were experimentally studied via Raman mapping measurements through UV irradiation. The photocatalytic ability decreased also orderly in the sequence of Ag-G-TiO2, G-Ag-TiO2, and Ag-TiO2-G, and the reason was discussed in details.

Anomalous bi-directional scanning electro-optic KTN devices with UV-assisted electron and hole injections

Abstract: In this Letter, we reported anomalous electro-optic potassium tantalate niobate (KTN) devices, in which both electrons and holes were injected into the KTN crystal via ultraviolet (UV) illumination-assisted charge injection. This could not only significantly enhance the performance of electro-optic devices (e.g., a 270% increase in the deflection angle in terms of the KTN deflector) but also enable the new bi-directional scanning capability. The results in this work would be very useful for a variety of devices and applications, such as electro-optic based vari-focal lenses.

Nanostructure enabled lower on-state resistance and longer lock-on time GaAs photoconductive semiconductor switches.

Abstract: We report a new, to the best of our knowledge, type of SI-GaAs photoconductive semiconductor switch (PCSS) with nanostructures. Since light can enter from both the top and side surfaces of nanostructures, the effective penetration depth is significantly increased. Lower on-state resistance and a longer lock-on time have been achieved in the nonlinear mode with this design, as well as a lower triggering fluence in the linear mode. This could be highly useful for a variety of applications that require lower on-state resistance and/or longer lock-on time such as pulsed power systems and firing set switches.

Enhanced electro-optic beam deflection of relaxor ferroelectric KTN crystals by electric-field-induced high permittivity

Abstract: Most applications of a ferroelectric-based electro-optic (EO) beam deflector have been limited by the high applied voltage. In this Letter, we report a dramatically increased EO beam deflection in relaxor ferroelectric potassium tantalate niobate (KTN) crystals by using the electric-field-enhanced permittivity. Due to the existence of the electric-field-induced phase transition in relaxor ferroelectric materials, the dielectric permittivity can be substantially increased by the applied electric field at a certain temperature. Both the theoretical study and the experimental verifications on the enhanced beam deflection and EO effect in the case with the electric-field-induced high permittivity were conducted. The experimental results confirmed that there was a three-fold increase in the deflection angle, which represented a dramatic increase in the deflection angle. By offering a wider deflection range and a lower driving voltage, such a largely enhanced beam deflection is of great benefit to the KTN deflector.

Flexible and Reusable Ag Coated TiO2 Nanotube Arrays for Highly Sensitive SERS Detection of Formaldehyde.

Abstract: Quantitative analysis of formaldehyde (HCHO, FA), especially at low levels, in various environmental media is of great importance for assessing related environmental and human health risks. A highly efficient and convenient FA detection method based on surface-enhanced Raman spectroscopy (SERS) technology has been developed. This SERS-based method employs a reusable and soft silver-coated TiO2 nanotube array (TNA) material, such as an SERS substrate, which can be used as both a sensing platform and a degradation platform. The Ag-coated TNA exhibits superior detection sensitivity with high reproducibility and stability compared with other SERS substrates. The detection of FA is achieved using the well-known redox reaction of FA with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT) at room temperature. The limit of detection (LOD) for FA is 1.21 × 10-7 M. In addition, the stable catalytic performance of the array allows the degradation and cleaning of the AHMT-FA products adsorbed on the array surface under ultraviolet irradiation, making this material recyclable. This SERS platform displays a real-time monitoring platform that combines the detection and degradation of FA.