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Manipulation of n and p type dope black phosphorene layer: A first principles study
손지철,Arqum Hashmi,Jisang Hong 한국물리학회 2016 Current Applied Physics Vol.16 No.5
We investigated the physical properties of the semiconducting impurity (Ga, Ge, As, and Se) doped phosphorene layer systems. The Ga and As doped layer showed a semiconducting behavior while the Ge doped system displayed a metallic state. The magnetic state appeared in the Se doped phosphorene. Deep donor or acceptor sates was found with doping of semiconducting impurities. To investigate an effective n and p type doped phosphorene, we explored the charge carrier doping effect. With an external electron carrier doping, the donor level induced by the Se impurity became an effective shallow donor level. Due to the Fermi level shifting, the metallic to semiconductor or vice versa was found in Ge and As. For external hole carrier doping, all the systems showed metallic band structures except for the Se doped structure. The Se impurity created a shallow acceptor state with an extra hole. Particularly, we propose that the most promising dopant is the Se because it creates a magnetic state in phosphorene and an extra electron or hole doping can induce an n-type or p-type phosphorene respectively. This suggests that the Se doped phosphorene has potential applications for both dilute magnetic semiconductor and p en junction device applications.
Optical Properties of g-C4N3/BN Bilayer Film: A First-principles Study
손지철,Arqum Hashmi,홍지상 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.9
Using first-principles method, we explored the frequency dependent dielectric function, refractive index, reflectivity, optical conductivity, loss function, and absorption coefficient of g-C4N3/BN bilayer system. Here, the dependences of the optical properties on the electric field polarization were also explored. Because the dielectric function strongly depended on the electric polarization, we obtained anisotropic optical properties. For instance, the dielectric function was frequency independent for perpendicular electric polarization while a frequency dependent dielectric function was observed for parallel electric polarization. A high refractive index larger than 2 was obtained for parallel polarization in the infrared and the visible frequency ranges, whereas a constant refractive index of approximately 1.5 was observed for perpendicular polarization. We found that the electromagnetic wave propagating perpendicular to the film surface had a very small reflectivity at ultraviolet frequencies, this property could be utilized for applications as anti-reflection ultraviolet coatings. In addition, the g-C4N3/BN bilayer may produce no meaningful joule heating for in-plane wave propagation because of its extremely weak optical conductivity. We propose that optical phonons may generated by incident ultraviolet waves. In addition, the bilayer system may be transparent in the visible range. Overall, we found that metal-free, transparent, half-metallic g-C4N3 films could be utilized for spintronics and optical device applications.
전립선비대증 환자에서 초음파를 이용한 방광 내 전립선 돌출과 방광벽 두께 측정의 유용성
김병훈,손지철,박철희,김천일 대한비뇨의학회 2005 Investigative and Clinical Urology Vol.46 No.11
Purpose: The objectives of this study were to evaluate whether intravesical protrusion of the prostate(IPP) and bladder wall thickness(BWT) are related to prostate volume(PV), prostate-specific antigen(PSA), International Prostate Symptom Score(IPSS) and bladder outlet obstruction (BOO) in patients with symptomatic benign prostatic hyperplasia(BPH). Materials and Methods: From September 2003 to May 2004, 152 patients with LUTS/BPH were included in this study. Their ages ranged from 46 to 86 years, with an average of 65.0 years. PV(measured by transrectal ultrasonography), serum PSA, IPSS, maximal flow rate(Qmax), post-voiding residual urine volume(PVR), acute urinary retention(AUR) and relationship with irritative or obstructive voiding symptoms were recorded. IPP and BWT were measured using transabdominal ultrasonography. The degree of protrusion was classified as grade I(less than 5mm), II(5 to 10mm) or III(greater than 10mm). The degree of thickness was classified as grade I(less than 5mm) or II(5mm or greater). Results: The higher IPP and BWT grades showed significant differences with higher PV, serum PSA and IPSS(p<0.05). Especially, higher BWT grade was associated with higher PVR and AUR(p<0.05). There were no statistically significant differences between grades and irritative or obstructive symptoms(p>0.05). Qmax showed no statistical significance between IPP and BWT(p>0.05). There was no correlation between IPP and BWT grades. Conclusions: IPP and BWT showed a statistically significant relation with PV, serum PSA and IPSS. Especially, higher BWT was associated with higher PVR and AUR. If symptomatic BPH patients receive medical treatment, IPP and BWT measurements appear to be useful predictors of BOO.
α-Fe<SUB>16</SUB>N<SUB>2</SUB>의 자기결정이방성
Imran Khan,손지철(Jicheol Son),홍지상(Jisang Hong) 한국자기학회 2016 韓國磁氣學會誌 Vol.26 No.4
We investigated the magnetocrystalline anisotropy of pure α-Fe<SUB>16</SUB>N<SUB>2</SUB> by using full-potential linearized augmented plane wave method (FLAPW). A very high magnetic moment was obtained for Fe (4d) site due to the lattice expansion in the z-direction, while the magnetic moment of Fe (4e) and (8h) site were suppressed due to hybridization with neighboring N atom. The calculated spin magnetic moments for different Fe sites (4d, 4e and 8h) were in good agreement with previously reported values. Due to the tetragonal distortion, we found a very large uniaxial anisotropy constant of 0.58 MJ/m3. Besides, a high value of magnetization of 1.76MA/m was obtained. In additon, the estimated coercive field and maximum energy product of 6.51 kOe and 71.7 MGOe were obtained for pure α-Fe<SUB>16</SUB>N<SUB>2</SUB>. This may suggest that the α-Fe<SUB>16</SUB>N<SUB>2</SUB> can be utilized for potential rare-earth free permanent magnet material.