http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Edge Oxidation Effect of Chemical-Vapor-Deposition-Grown Graphene Nanoconstriction
Iqbal, Muhammad Waqas,Iqbal, Muhammad Zahir,Jin, Xiaozhan,Hwang, Chanyong,Eom, Jonghwa American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.6
<P>The edge oxidation effects of chemical-vapor-deposition-grown graphene devices with nanoconstrictions of different sizes are presented. The effects of edge oxidation on the doping level of a nanoconstriction graphene device were identified by Raman spectroscopy and using the back-gate-voltage-dependent resistance. Strong p-type doping was observed as the size of nanoconstriction decreased. The Dirac point of the graphene device shifted toward positive voltage, and the positions of the G and 2D peaks in Raman spectroscopy shifted toward a higher wave number, indicating the p-type doping effect of the graphene device. p-type doping was lifted by deep-ultraviolet light illumination under a nitrogen atmosphere at room temperature. p-type doping was restored by deep-ultraviolet light illumination under an oxygen atmosphere at room temperature. Edge oxidation in the narrow structures explains the origin of the p-type doping effect widely observed in graphene nanodevices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-6/am405885c/production/images/medium/am-2013-05885c_0008.gif'></P>
Deep-ultraviolet-light-driven reversible doping of WS2 field-effect transistors.
Iqbal, Muhammad Waqas,Iqbal, Muhammad Zahir,Khan, Muhammad Farooq,Shehzad, Muhammad Arslan,Seo, Yongho,Eom, Jonghwa RSC Pub 2015 Nanoscale Vol.7 No.2
<P>Improvement of the electrical and photoelectric characteristics is essential to achieve an advanced performance of field-effect transistors and optoelectronic devices. Here we have developed a doping technique to drastically improve electrical and photoelectric characteristics of single-layered, bi-layered and multi-layered WS2 field-effect transistors (FET). After illuminating with deep ultraviolet (DUV) light in a nitrogen environment, WS2 FET shows an enhanced charge carrier density, mobility and photocurrent response. The threshold voltage of WS2 FET shifted toward the negative gate voltage, and the positions of E and A1g peaks in Raman spectra shifted toward lower wavenumbers, indicating the n-type doping effect of the WS2 FET. The doping effect is reversible. The pristine characteristics of WS2 FET can be restored by DUV light illumination in an oxygen environment. The DUV-driven doping technique in a gas environment provides a very stable, effective, easily applicable way to enhance the performance of WS2 FET.</P>
Content-based Image Retrieval Using Haar Wavelet Transform and Color Moment
Iqbal Hasan Sarker,Shahed Iqbal 한국산학기술학회 2013 SmartCR Vol.3 No.3
Content-based image retrieval (CBIR) deals with the retrieval of most similar images corresponding to a query image from an image database by using visual contents of the image itself. It requires feature extraction and computation of similarity. In this paper, we propose a content-based image retrieval method that uses a combination of color and texture features. The Haar wavelet transform is used for texture feature extraction, and for color feature extraction we use color moments. The distance between the query image features and the database images’ features is computed by using Canberra distance. We assign weights to texture feature distance and color feature distance and calculate the similarity with combined feature distance. Experiment results reflect the importance of the Haar wavelet transform and color moments in the performance of our proposed CBIR method.
Iqbal, M.Z.,Kelekci, O.,Iqbal, M.W.,Eom, J. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.59 No.-
The defect formation mechanism in chemical vapor deposition grown single layer graphene devices has been investigated by increasing electron beam (e-beam) irradiation doses gradually up to 750e<SUP>-</SUP>/nm<SUP>2</SUP>. The evolution of D peaks in Raman spectra provides an evidence of strong lattice disorder due to e-beam irradiation. Particularly, the trajectory of D and G peak intensities ratio (I<SUB>D</SUB>/I<SUB>G</SUB>) suggests that the transformation of graphene from crystalline to the nanocrystalline and then towards amorphous form with increasing irradiation dose. The defect parameters were calculated by phenomenological model of amorphization trajectory for graphitic materials. The mobility decreasing gradually from ~1200 to ~80cm<SUP>2</SUP>/V s with gradual increase of irradiation dose, which implies the formation of localized states in e-beam irradiated graphene. The Dirac point is shifted towards negative gate voltage which indicates the n-doping in graphene with increasing e-beam irradiation dose.
Modification of the structural and electrical properties of graphene layers by Pt adsorbates
Iqbal, M Waqas,Iqbal, M Zahir,Khan, M Farooq,Jin, Xiaozhan,Hwang, Chanyong,Eom, Jonghwa TaylorFrancis 2014 SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS Vol.15 No.5
<P>The properties of graphene are strongly affected by metal adsorbates and clusters on graphene. Here, we study the effect of a thin layer of platinum (Pt) metal on exfoliated single, bi- and trilayer graphene and on chemical vapor deposition-grown single-layer graphene by using Raman spectroscopy and transport measurements. The Raman spectra and transport measurements show that Pt affects the structure as well as the electronic properties of graphene. The shift of peak frequencies, intensities and widths of the Raman bands were analyzed after the deposition of Pt with different thicknesses (1, 3, 5 nm) on the graphene. The shifts in the G and 2D peak positions of the Raman spectra indicate the n-type doping effect by the Pt metal. The doping effect was also confirmed by gate-voltage dependent resistivity measurements. The doping effect by the Pt metal is stable under ambient conditions, and the doping intensity increases with the increasing Pt deposition without inducing a severe degradation of the charge carrier mobility.</P>