Development of an active-matrix "HEED" cold cathode and its application to an image sensor
For practical advantages of the HEED (high-efficiency electron emission device) such as a low driving voltage, a high emission current density, especially application to an ultra high sensitive compact image sensor can be expected. A prototype active-matrix HEED image sensor integrated with scanning driver circuits was developed with a HARP (high-gain avalanche rushing amorphous photoconductor) target. It was demonstrated that the prototype 256 times 192 pixels active-matrix HEED array operates well as an effective probe for high-resolution image pickup under dim lighting. The possibility of the active-matrix HEED for development of next-generation image sensor with ultra high sensitivity and high definition was concluded in this report
High Efficiency Electron-Emission in Pt/SiOx/Si/Al Structure
A high efficiency electro-emission device (HEED) has been developed with a structure of Pt/SiOx /Si/Al on a thermally-oxidized Si substrate. The thicknesses of the SiOx and Si films were 400 nm and 5 µ m, respectively. Electron emission characteristics of the HEED are reported. It was found that the HEED has an electron-emission efficiency as high as 28% and a high brightness of 80 kcd/m2 using phosphor ZnS:Cu,Al. This high electron-emission efficiency was obtained in a range of applied voltage in which negative resistance occurred.
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.