Electrical and magnetotransport properties of single walled carbon nanotube (SWCNT) fibers are reported. The dependencies of resistance on temperature can be approximated by the Mott law for three-dimensional variable range hopping (VRH) below 80 K and by typical law for fluctuation induced tunneling model within the range of 80–300 K. Both negative and positive magnetoresistances (MRs) were observed. At low fields, MR is negative. Positive upturn was observed on the MR curves, which shifted to the high field’s values with temperature increase. The upturn field of the MR effect was shifted from 1.5 T at 2 K to a value of about 20 T at 40 K. The value of positive MR varies as exp(B2), which changes to B1/3 at sufficiently high fields as expected for the VRH transport. The model of VRH transport is illustrated by the influence of strong microwave field and terahertz radiation induced photocurrent manifestation at low temperatures.
The electrical characteristics of power MOSFETs additionally implanted with nitrogen ions have been studied. Ion implantation of nitrogen was carried out through a protective oxide of 23 nm thickness with energies of 20 and 40 keV and doses of 1 ⋅ 1013‒5 ⋅ 1014 cm–2. Rapid thermal annealing was carried out at temperature of 900 or 1000 °C for 15 s. It has been established that nitridisation of the gate dielectric makes it possible to reduce the noise of the gate leakage currents and their dispersion. In the direct order of heat treatment (first rapid thermal annealing, and then the removal of the protective oxide), for samples prepared with an additional operation of nitrogen ion implantation, there is an increase in the threshold voltage compared to control samples. The capacitance of the gate dielectric in the case of implantation of nitrogen ions in the direct order of heat treatment is less than for control samples. It has been established that in the direct order of rapid thermal annealing, the doses of nitrogen ion implantation do not cause significant changes in the maximum value of the current-voltage slope. At the same time, in all studied cases, there is a shift in the maximum value of the current-voltage slope towards higher gate voltages. In the reverse order of heat treatment (first the removal of the protective oxide, and then rapid thermal annealing), there are no significant differences in the value of the threshold voltage for the samples created with additional nitrogen implantation and the control ones. The maximum value of the current-voltage slope also does not experience significant changes. It is shown that in the voltage range from – 0.15 to 0 V, the drain current of nitrogen-implanted samples manufactured using the direct order of heat treatment is higher than for control samples, and the drain current of nitrogen-implanted samples obtained with the reverse order of heat treatment it is lower compared to control samples. Results are explained by a decrease in the density of surface states at the Si – SiO2 interface in MOS-structures created using an additional operation of nitrogen ion implantation in the direct order of heat treatment.
Power MOS-transistors with vertical structure are investigated. Additionally, in some devices, ion implantation of nitrogen with energies of 20 and 40 keV was carried out in a dose range of 1 ⋅1013–5 ⋅ 1014 cm –2 through a sacrificial oxide 20 nm thick. For one group of wafers, rapid thermal annealing was first carried out, then oxide removal (forward order), for the other group – in the opposite sequence (reverse order). It was found that with the additional doping of nitrogen ions in doses of 1⋅1013–5 ⋅ 1013 cm –2 with energy of 20 keV, an increasing of gate dielectric charge to breakdown for both types of annealing is observed. The maximum effect occurred for the samples at a dose of nitrogen ions of 1⋅1013 cm –2 with the forward heat treatment order. This is due to the interaction of nitrogen atoms with dangling bonds of the Si – SiO2 interface during annealing, as a result of which strong chemical bonds are formed that prevent charge accumulation on the surface of the Si – SiO2 interface. It is assumed that the main contribution to the gate leakage current is made by the tunneling of charge carriers through traps.
We measure the reflectance spectra of 1.8 μm-thick FP9120 photoresist films doped with antimony ions and deposited by centrifugation on the surface of p-type silicon wafers (ρ = 10 Ω cm) with a (111) orientation. Implantation leads to a decrease in the refractive index of the photoresist due to the radiation crosslinking of Novolac resin molecules and a decrease in the molecular refraction and density of the photoresist. In the opacity region of the photoresist film, an increase in the reflection coefficient is observed with an increase in the implantation dose.
Studies have been carried out by time-of-flight mass spectroscopy of secondary ions of subcutaneous silicon oxides, nitridation by ion implantation (II) or nitrided by high-temperature annealing in an atmosphere of N2. Nitrogen AI was produced with an energy of 40 keV, implantation doses of 2,5×1014 and 1×1015 cm-2. High-temperature annealing was carried out at a temperature of 1200 C for 2 hours or at 1100 C for 30 minutes. It is established that at the Si–SiO2 interface, after nitriding by II or high-temperature annealing, a maximum with a high concentration of nitrogen atoms is observed. It is shown that after conducting nitrogen AI with a dose of 2,5 ×1014 cm-2 through a protective SiO2 with a thickness of 23 nm and RTA at 1000 C for 15 seconds, the main maximum of nitrogen distribution (1×1019 cm-3) is observed at the Si–SiO2 interface, which indicates the presence of a saturation concentration of the Si–SiO2 interface. A charge-based one-dimensional Fermi model is proposed to describe the accelerated diffusion of nitrogen atoms. The main mechanism is the diffusion of interstitial atoms, which can occur with the preliminary displacement of nodal nitrogen atoms by their own embedding atoms. It is shown that nitrogen atoms can act as annihilation centers of point defects in the silicon crystal lattice.
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