Effect of Defect Bands on the Electrical Characteristics of Irradiated GaAs and
Proton bombarded p-Si and neutron irradiated n-GaAs have been studied by DLTS, current±voltage, and capacitance±voltage measurements in metal±semiconductor junctions. The junctions were prepared by evaporation of Al onto silicon and of gold onto GaAs. Both junctions exhibited defect bands after bombardment. The bombardment has shifted the Fermi-level pinning position, increased the ideality factor in both junctions, and also affected the temperature dependence of the ideality factor and that of the capacitance. The results show that the main effect of the radiation is the generation of laterally inhomogeneous defects near the semiconductor surface.
Effect of Defect Bands on the Electrical Characteristics of Irradiated GaAs and Si
Proton bombarded p-Si and neutron irradiated n-GaAs have been studied by DLTS, current–voltage, and capacitance–voltage measurements in metal–semiconductor junctions. The junctions were prepared by evaporation of Al onto silicon and of gold onto GaAs. Both junctions exhibited defect bands after bombardment. The bombardment has shifted the Fermi-level pinning position, increased the ideality factor in both junctions, and also affected the temperature dependence of the ideality factor and that of the capacitance. The results show that the main effect of the radiation is the generation of laterally inhomogeneous defects near the semiconductor surface.
Recent progress in engineering near-infrared persistent luminescence nanoprobes for time-resolved biosensing/bioimaging
Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation. Due to the ultra-long decay time of persistent luminescence (PersL), autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely, thus the imaging contrast and sensing sensitivity can be significantly improved. Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues, near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging. In this review, we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging, such as transition metal ions-doped NIR PLNPs, lanthanide ions-doped NIR PLNPs, organic molecules-based NIR PLNPs, and semiconducting polymer self-assembled NIR PLNPs. Notably, organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs, for the first time, were introduced to the review of PLNPs. Secondly, the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism. It includes the regulation of valence band and conduction band of different host materials, alteration of defect types, depth and concentration changes caused by ion doping, effective radiation transitions and energy transfer generated by different luminescence centers. Given the design and potential of NIR PLNPs as long-lived luminescent materials, the current challenges and future perspective in this rapidly growing field are also discussed.