Transition Metal-Doped ZnO Nanowires: En Route Towards Multi-colour Light Sensing and Emission Applications

Abstract

368and strength of the chemical bonds of wide-band gap semiconductors, photodetectors engineered based on most of metal-oxides can withstand highly elevated T and hostile environments. Despite the fact that carrier mobilities are much smaller in cases of metal oxides compared with those of many conventional semiconductors, owing to the drastically increased dielectric strength of metal oxides, much larger carrier velocities can be readily achieved by applying much higher electric fields/device biases. The property remains critical for reducing the photogenerated carrier transit time and thus improving gain characteristics of the photodetectors. Advances in nanofabrication methodologies now allow growing many metal-oxide nanowires, including in ZnO as dislocation-free, highly faceted single crystals, which according to the above-made discussion show significant promise for diverse nanophotodetector device as well as light-emission applications. At the same time, compared to cSi, ZnO nanowires typically exhibit a very limited intrinsic sensitivity to visible and infrared radiation, whereas the sensitivity to short-wavelength photons also tends to be reduced as a result of their small diameter and relative increase in the number of the surface defect states. In this chapter, we provide a brief review on the progress in engineering highresponsitivity ZnO nanowire photodetectors operating in an extended, i.e., ultravioletvisible spectral range. Particular attention is paid to the use and role of transition metal dopants to enhance the light sensitivity of ZnO nanowires/nanorods grown by seeded vapor-transport methods. Detailed consideration is given to several key aspects pertaining to the transport, photoconduction, and time-response characteristics of two-terminal metalsemiconductor-metal nano-photodetectors operating at both pre-avalanche and avalanche regimes. This review might be important to scientists working in with high-sensitivity and multispectral oxide-based nano-photodetectors, optical switches, and sensors.

Probing luminescent Fe-doped ZnO nanowires for high-performance oxygen gas sensing application

“…2 Moreover, the band-to-band electronic transitions are enhanced by Fe-doping at lattice sites for reducing charge trapping. 15 In the present work, a luminescent Fe-doped ZnO nanowire based oxygen gas sensor has been investigated for fast response/ recovery time. The ZnO nanowires were synthesized by employing an alternative approach using Fe and Zn as starting materials in a controlled environment for the growth of free standing Fe-doped ZnO nanowires in contrast to the catalyst coated substrates used for obtaining ZnO nanowires during a typical vapour phase transport process.…”

ОБРАЗОВАНИЕ ЗАРЯЖЕННЫХ СОСТОЯНИЙ НА ПОВЕРХНОСТИ ZnO ПРИ НИЗКОЭНЕРГЕТИЧЕСКОМ ОБЛУЧЕНИИ ЭЛЕКТРОНАМИ

“…(1) Также на кривой 1 наблюдается слабое формирование нескольких пиков при энергиях возбуждения 2, 4, 6, 8, 12 и 14 эВ. Основные максимумы в спектрах обозначены буквами А, Б, В, Г и Д. Максимум А при энергии 2.5 эВ в спектре ПТ показывает наличие дорадиационных дефектов (вакансий кислорода в поверхностных слоях ZnO) [17][18][19]. Достаточно большое количество работ посвящено исследованию пика А в образцах нелегированного ZnO, который располагается в области спектра, связанной с собственными дефектами, и имеет максимум около 2.0−2.5 эВ.…”

“…Далее при энергиях облучения 20 эВ (кривая 3) появляется максимум А при энергии 1.5 эВ, также исчезает максимум Г при энергии 8 эВ. Образование максимумов А при энергии 1.5 эВ на энергетической оси (максимум при 1.5 эВ − вакансии цинка, поверхностная дырка по данным [17]) указывает на то, что начинается образование вакансии цинка. Также исчезновение из спектров ПТ максимума Г при энергии 8 эВ показывает снижение концентрации атомов цинка на границе раздела и доминирование атомов кислорода на поверхности (максимум Д при энергии 12 эВ).…”