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Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
What are the special properties of semiconductors that make their study important to us? The electrical conductivity of semiconductors can be altered by the controlled addition of a small amount of impurities. This controlled addition of impurities to a pure semiconductor material, called an intrinsic semiconductor, is known as doping.
Unable to Resist
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
At room temperature, the second term in equation 6.17 is so much smaller than the bandgap that the Fermi level is very close to the middle of the bandgap. The Fermi level will, however, be exactly in the middle of the bandgap no matter what the temperature of the intrinsic semiconductor is if NC = NV. (This is because ln 1 = 0.) If the density of states in one of the bands is much larger than that of the other, for example, as we saw in the last subsection NC for silicon is larger than NV, then the Fermi level will no longer be found in the middle of the gap. In the case of silicon, for example, it will be below the middle. In all cases, the Fermi energy of an intrinsic semiconductor can be described as the “intrinsic Fermi level” and denoted by Ei.
Electrical Field in Materials
Published in Ahmad Shahid Khan, Saurabh Kumar Mukerji, Electromagnetic Fields, 2020
Ahmad Shahid Khan, Saurabh Kumar Mukerji
The electrical conductivities of semiconducting materials fall in between those of conductors and insulators and can be widely varied by changing their temperature, excitation, and impurity contents. These lie roughly in the range of 10−2 to 104 Siemens per centimeter (S·cm−1). The transport of charges through a semiconductor is not only the function of properties of electrons but strongly linked to the arrangement of atoms in solids. The pure semiconductor is referred to as an intrinsic semiconductor. Semiconductors mixed with impurities can be classified in terms of type of impurity. These impurities, also called extrinsic materials, are referred to as n- or p-type. The n (or negative) type materials are those wherein electrons are in excess whereas in p (or positive) type holes are in excess. Thus in n-type, electrons are the charge carriers and in p-type, holes are the charge carriers. Holes, the mobile positive charge carriers are identified as the places where a valence electron is missing in the semiconducting crystal.
The effect of VOC and environmental parameters on ozone sensors performance
Published in Advances in Building Energy Research, 2023
Mahsa Ghasemi, Fariborz Haghighat, Chang-Seo Lee, Marzieh Namdari
The presence of interfering compounds such as , CO and VOCs can also affect the measurement of ozone concentration by semiconductor monitors (Korotcenkov et al., 2018). Rai et al. (2017) reported that the response of semiconductor ozone sensors in the presence of CO changed significantly and CO was recognized as one of the important interfering compounds for this type of sensor. Korotcenkov et al. (2018) showed that the presence of 2, CO and humidity in the air does not have much effect on semiconductor sensors and it is suitable for ozone detection in a natural environment and has better selectivity than semiconductor sensors. Prajesh et al. (2019) examined the resistance of a semiconductor sensor at different airflow rates in an environmental chamber. The results illustrated that sensor resistance increased with increasing the airflow rate and conductivity decreased with increasing oxygen partial pressure. As noted in some studies, conductivity of semiconductor sensors depends on oxygen partial pressure, and with increasing partial pressure conductivity and resistance of n-type semiconductors reduces and increases, respectively. The opposite manner is expected for the p-type ones (Felix et al., 2016; Karnati et al., 2019; Prajesh et al., 2019). Generally, Semiconductors are divided into Intrinsic and extrinsic. An intrinsic semiconductor is the pure form of semiconductor, while in an extrinsic semiconductor like n-type (pentavalent impurity is added) and p-type (trivalent impurity is added), impurities are added intentionally to make it conductive (Eranna et al., 2004).