Research Progress of Two-dimensional Matrix Detectors in IMRT Dose Verification

With the continuous development of science and technologies in China, radiotherapy technology in medical field has been very significantly developing, and intensity modulated radiation therapy (IMRT) technology has been the most widely used. This paper first introduces the components and types of two-dimensional matrix detector, two-dimensional ionization chamber matrix detector and two-dimensional semiconductor matrix detector, then analyzes the dosimetric characteristics of the two-dimensional matrix detector. In the end, the various applications of the two-dimensional matrix detector are analyzed and discussed in detail. The paper aims to promote the two-dimensional matrix detector’s development in the field of radiotherapy in China.

Fidelity of noisy multiple-control reversible gates

The effect of frequency noise on correct operation of the multiple-control Toffoli, Fredkin, and Peres gates has been discussed. In the framework of the Ising model, the energy spectrum of a chain of atoms with nuclear spins one-half in a spinless semiconductor matrix has been obtained, and allowed transitions corresponding to the operation algorithm of these gates have been determined. The fidelities of the obtained transitions were studied depending on the number of control qubits and parameters of the radio-frequency control pulses. It has been shown that correct operation of the Toffoli and Fredkin gates does not depend on the number of control qubits, while the Peres gate fidelity decreases significantly with the increasing number of control signals. The calculated ratios of the Larmor frequency to the exchange interaction constant correspond with the results of other studies.

Fabrication of Microbolometer Arrays Based on Polymorphous Silicon–Germanium

This work reports the development of arrays of infrared sensors (microbolometers) using a hydrogenated polymorphous silicon–germanium alloy (pm-SixGe1-x:H). Basically, polymorphous semiconductors consist of an amorphous semiconductor matrix with embedded nanocrystals of about 2–3 nm. The pm-SixGe1-x:H alloy studied has a high temperature coefficient of resistance (TCR) of 4.08%/K and conductivity of 1.5 × 10−5 S∙cm−1. Deposition of thermosensing film was made by plasma-enhanced chemical vapor deposition (PECVD) at 200 °C, while the area of the devices is 50 × 50 μm2 with a fill factor of 81%. Finally, an array of 19 × 20 microbolometers was packaged for electrical characterization. Voltage responsivity values were obtained in the range of 4 × 104 V/W and detectivity around 2 × 107 cm∙Hz1/2/W with a polarization current of 70 μA at a chopper frequency of 30 Hz. A minimum value of 2 × 10−10 W/Hz1/2 noise equivalent power was obtained at room temperature. In addition, it was found that all the tested devices responded to incident infrared radiation, proving that the structure and mechanical stability are excellent.

High-Temperature Ferromagnetism of Zn1-xMnxOy Thin Films Synthesized by Pulsed Laser Deposition

The paper discusses the findings of the study of the structural and magnetic properties of Zn1-xMnxOy thin films (x = 0-0.08), synthesized by pulsed laser deposition under different conditions. It has been discovered that during the doping, thin films remain single-phased and retain wurtzite structure (ZnO wurz), oriented along the direction (001). It has been determined that thin films obtained under the same synthesis conditions have similar crystallite sizes, which is confirmed by the substitution of Mn2+ ions with Zn2+ ions in the Zn O semiconductor matrix. It has been found that annealing of samples in the oxygen atmosphere increases the surface roughness from 1-3 nm to ~ 10 nm; the higher the concentration of manganese in Zn1-xMnxOy films is, the greater the value of Ra. It has been demonstrated that, at room temperature, all Zn1-xMnxOy thin films (x = 0-0.08) exhibit ferromagnetic behavior, which is more pronounced upon the increase in concentration of oxygen vacancies and manganese in the samples. It is assumed that two mechanisms explaining high-temperature ferromagnetism coexist in the films: the first one is determined by ferromagnetic exchange between Mn2+ cations by means of oxygen vacancies, the second one deals with super-exchange interaction between oxygen vacancies.

Фотолюминесценция квантовых точек Zn-=SUB=-1-x-y-=/SUB=-Cu-=SUB=-x-=/SUB=-Eu-=SUB=-y-=/SUB=-S/EuL-=SUB=-3-=/SUB=- в полиакрилатной матрице

Zinc sulfide is one of the most popular luminescent semiconductors of group A(II)B(VI). Doping ZnS quantum dots with Ln3+ ions makes it possible to form nanoscale structures in a semiconductor matrix containing isolated centers of narrow-band luminescence. The introduction of quantum dots into the acrylate matrix further stabilizes the particles and allows them to form their morphology. Nanoscale structures of Zn1-x-yCuxEuyS/EuL3, where L − trifluoroacetate are anions, were synthesized by the method of emerging reagents in situ in the medium of methyl methacrylate (MMA). ZnS doping was performed by simultaneous introduction of soluble precursors of zinc sulfide, as well as copper and europium trifluoroacetates into the acrylate reaction mixture. Polymer optically transparent compositions of PMMA/Zn1-x-yCuxEuyS/EuL3 were obtained by radical polymerization of MMA in the block. The excitation of luminescence of compositions is associated with Interzone electron transitions in ZnS, with a system of levels that form alloying ions in the forbidden zone of ZnS, as well as with their own energy absorption by Eu3+ ions. Broadband luminescence of compositions is caused by intracrystalline defects formed in ZnS during doping. Narrow-band luminescence occurs as a result OF 5D0→7Fj electronic transitions in Eu3+ ions associated with quantum dots, as well as being in the polymer matrix independently of them. The transfer of energy from the donor levels of the semiconductor matrix to the levels of Eu3+ ions, followed by its release in the form of luminescence, was confirmed by the imposition of absorption bands doped with ZnS and excitation bands of luminescence compositions, as well as an increase in the intensity of narrow-band luminescence of Eu3+ ions while reducing the intensity of a wide band of recombination luminescence of doped ZnS. A decrease in the intensity of the ZnS recombination luminescence band with an increase in the concentration of Eu3+ >1.0∙10-3 mol/L ions is also associated with the formation of a layer of complex europium compounds on the particle surface that prevent the passage of exciting radiation to the particle core.

Параметры полупроводниковых пленок ZnO, легированных 3d-примесями Mn, Fe

The effect of Fe and Mn impurities on the magnetic parameters of ZnO wide-gap semiconductor films produced by high-frequency sputtering with wide variations in the defect concentration is studied. The introduction of Mn and Fe magnetic impurities brings about the existence of a magnetically ordered state in the semiconductor matrix, with different positions of the axis of easy magnetization. In the case of doping with Mn, this axis lies perpendicularly to the film plane, and in the case of doping with Fe, this axis lies in the film plane.

О фазовом разделении в слоях (Ga,Mn)As, полученных ионной имплантацией и последующим лазерным отжигом

In this paper, we present the results of studies of the spectral, temperature, and field dependences of the transversal Kerr effect in Ga_1 – _ x Mn_ x As ( x = 0.0066–0.033) layers produced by ion implantation and subsequent pulsed laser annealing. The complicated nonmonotonous nature of the temperature dependences of the transversal Kerr effect and its dependence on the measurement range indicate a magnetic inhomogeneity of the layers. The reasons for the inhomogeneity can be the Gaussian distribution of Mn over the thickness of the layers and the electron phase separation in them. The appearance of new features in the spectra of the transversal Kerr effect is explained by the presence in the doped semiconductor matrix of nanoregions with a higher carrier concentration and a higher Curie temperature and a shift of the Fermi level into the valence band leading to an increase in the energy of optical transitions.

Вариативность результирующего поля микродеформаций в кристаллах Zn-=SUB=-1-x-=/SUB=-V-=SUB=-x-=/SUB=-Se (0.01≤ x≤0.10)

A detailed neutronographic study of the bulk ZnSe crystals doped with vanadium up to the content commensurate with the solubility limit in a semiconductor matrix has been carried out for the first time at room temperature. The data that characterize nonuniformly-deformed states based on the cubic structural modification of the II–VI compounds are obtained. A simplified analysis of the broadening patterns of the diffraction profiles of main Bragg reflexes of the studied crystals shows that the resulting deformation covers macroscopic volumes, and the distribution of vanadium ions in the given cases may significantly deviate from the uniform distribution over volume. Relative to the initial cubic lattice, dominating trends towards symmetry changes preceding the phase stratification in the ZnSe crystals heavily doped with vanadium are revealed.