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Light-Emitting Devices Based on Direct Band Gap Semiconductor Nanoparticles
Published in Claudia Altavilla, Enrico Ciliberto, Inorganic Nanoparticles: Synthesis, Applications, and Perspectives, 2017
Ekaterina Neshataeva, Tilmar Kümmell, Gerd Bacher
Successful substitution of the organic support layers opened a path for all-inorganic QD-LED. One of the first all-inorganic devices was presented by Artemyev et al. in year 1997, where no additional support layers were used (Artemyev et al. 1997). CdS nanocrystals were drop-deposited in a 200–300 nm thick layer between ITO and Ag electrodes. Spectrally wide EL with a voltage-dependent color was achieved at voltages higher than 20 V. The resulting EL spectrum was attributed to voltage-controlled population of different deep trap states. The overall efficiency and brightness were poor. Nevertheless, EL could be observed by a naked eye. Improved structures with inorganic charge injection/transport support layers were recently reported (Mueller et al. 2005; Caruge et al. 2008; Kang et al. 2008; Gopal et al. 2009). Caruge et al. (2008) demonstrated an efficient all-inorganic QD-LED with sputtered metal-oxide charge transport layers. Figure 5.11 shows a schematic of the QD-LED with NiO hole- and alloyed ZnO and SnO2 ETLs (a) and the corresponding band diagram determined from UV photoemission spectroscopy and optical absorption measurements (b). The EQE and luminosity of the device as a function of the current density are shown in Figure 5.11c with a photograph of the device, operated at 6 V bias as an inset, demonstrating the efficiency and high robustness of the inorganic charge transport layers. Not only NiO (Caruge et al. 2008) but also p-type Si (Kang et al. 2008; Gopal et al. 2009) and p-type GaN (Mueller et al. 2005) were used as hole injection and transport layers. On the electron injection side, besides ZnO:SnO2 (Caruge et al. 2008; Gopal et al. 2009), n-type GaN (Mueller et al. 2005) and n-type TiO2 (Kang et al. 2008) have been applied. The active QD layer was deposited by either a Langmuir-Blodgett-method (Mueller et al. 2005), spin coating (Caruge et al. 2008; Kang et al. 2008), or contact printing (Gopal et al. 2009). The deposition of the inorganic support layers was more laborious with various deposition techniques, such as energetic neutral atom beam lithography/epitaxy (Mueller et al. 2005), plasma-enhanced metallorganic chemical vapor deposition (Kang et al. 2008), and sputtering (Caruge et al. 2008; Gopal et al. 2009). These deposition techniques require chambers with controlled pressure, gas flow, and temperatures sometimes up to 500°C (Mueller et al. 2005), which makes the fabrication of large-area emitters on flexible substrates challenging. The simplification of the inorganic layer deposition techniques by utilizing appropriate inorganic nanoparticles might be one key issue for future devices.
Charge transfer of keV-energy H+ ions in grazing scattering on Cu(100)
Published in Radiation Effects and Defects in Solids, 2023
Wenhao Liang, Yanghui Weng, Yue Guo, Guang Zhong, Lei Wan, Hong Lin, Bin Ding, Luyao Zhang, Jiawei Wang, Yanling Guo, Lin Chen, Ximeng Chen, Zhen Yang
The problem of energy shortage is a serious problem facing mankind today. Thermonuclear reactor is considered as the ultimate solution to this problem (1). For large magnetic confinement fusion devices, such as International Thermal Experimental Reactor (ITER), the neutral beam injection (NBI) system produced by strong current negative hydrogen ion sources can provide ignition and heating for plasma (2–4). The inherent problems of cesium use, i.e. the long-term operation stability, have promoted the development of cesium free negative ion sources in recent years (5–10), and the extreme performance requirement is closely related to the efficient formation mechanism of negative ions. In addition, the observation of energetic neutral atoms (ENAs) can provide information about the density, volume velocity and energy distribution of the Local Interstellar Medium, which is very interested in space and planetary science. In the low-energy ENA imaging instruments, scattering on the charge state conversion surface by grazing incidence has become a major way to convert neutral atoms into ions for detection (11–14). Thus the conversion efficiency or the charge states fraction is needed to determine the yield of ENAs.