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Theory of photon detectors
Published in Antoni Rogalski, Infrared and Terahertz Detectors, 2019
The surface of actual devices is passivated so as to stabilize the surface against chemical and heat-induced changes as well as to control surface recombination, leakage, and related noise. Native oxides and overlying insulators are commonly employed in p-n junction fabrication that introduces fixed charge states, which then induce accumulation or depletion at the semiconductor–insulator surface. We can distinguish three main types of states on the semiconductor–insulator interface, namely, fixed insulator charge, low surface states, and fast surface states. The fixed charge in the insulator modifies the surface potential of the junction. A positively charged surface pushes the depletion region further into the p-type side and a negatively charged surface pushes the depletion region toward the n-type side. If the depletion region is moved toward the more highly doped side, the field will increase, and tunneling becomes more likely. If it is moved toward the more lightly doped side, the depletion region can extend along the surface, greatly increasing the depletion region–generated currents. When sufficient fixed charge is present, accumulated and inverted regions as well as n-type and p-type surface channels are formed (see Figure 12.21) [95]. An ideal surface would be electrically neutral and would have a very low density of surface states. The ideal passivation would be a wide gap insulator grown with no fixed charge at the interface.
Basic Materials Engineering
Published in David A. Hansen, Robert B. Puyear, Materials Selection for Hydrocarbon and Chemical Plants, 2017
David A. Hansen, Robert B. Puyear
Carbon steel and stainless steels are among the common alloys that can be passivated. Passivation consists of exposing the clean metal surface to an oxidizing environment. The resulting passivated surface is much more corrosion resistant than it would be in an unpassivated state. Passivation is thought to be associated with the formation of an oxide film. In materials such as carbon steel, which form relatively weak oxides, passivation can be destroyed rather easily. In oxide-stabilized alloys such as the stainless steels, passivation-induced corrosion resistance is not easily destroyed, especially in oxidizing environments.
Assembly Techniques
Published in Roydn D. Jones, Hybrid Circuit Design and Manufacture, 2020
The flip chip is a passivated semiconductor chip which has small solder bumps on its termination pads. The passivated surface gives environmental protection to the device. Figure 8.3 shows a typical device configuration.
Highly efficient capture of mercury from complex water matrices by AlZn alloy reduction–amalgamation and in situ layered double hydroxide
Published in Environmental Technology, 2023
Yetian Fang, Fangyuan Li, Jingbo Chao, Yang Tang, Frederic Coulon, Patrycja Krasucka, Patryk Oleszczuk, Qing Hu, Xiao Jin Yang
The passivation is a critical factor affecting the performance/reactivity of zerovalent metals, bimetals and alloys for water remediation, due primarily to the formation of metal oxides and hydroxides, which are considered to improve adsorption of pollutants and on the other hand, to passivate the surface. In this context, AlFe alloys (10, 20 and 50% Fe) were also investigated along with zerovalent Fe and Al in this study (see Supplemental Material Section I – Supplemental text Section I and Figures S5–S11). The findings of AlFe alloy investigations are (1) Hg(II) removal rate increases with Fe concentration for 10 mg L−1 Hg(II) at initial pH 2 and the highest rate of 99.6% is achieved by Fe(0), which simultaneously releases Fe ion concentration as high as 320 mg L−1; (2) both Al(0) and Fe(0) in the AlFe alloys provide electrons for Hg(II) reduction in acidic medium while Al(0) is the sole electron donor in alkaline pH medium; (3) the intermetallic compounds like Fe4Al13 in AlFe alloys play an important role in catalyzing Hg(II) reduction, improving the durability and reducing leached concentrations of Al and Fe ions.
A brief insight into the use of plant products as green inhibitors for corrosion mitigation of aluminium and aluminium alloys
Published in Canadian Metallurgical Quarterly, 2022
K Namitha, Padmalatha Rao, Suma A. Rao
Corrosion features of aluminium and its alloys are of considerable interest for investigators because of their technical and engineering prominence [9]. Aluminum and its alloys are highly corrosion resistant in many environments. This is due to the formation of passivating oxide layer [10]. If ruptured, the oxide film reforms rapidly. But a change in the environment may cause the passivated metal to revert to an active state. Pourbaix diagram (Figure 1), in destructive media, with pH ranging from 3.6–8.9, the oxide layer gets depleted off, and metal dissolution continues [11].