Enhanced Optical and Electrical Properties of Boron-doped Zinc-oxide Thin Films Prepared by Using the Sol-gel Dip-coating Method

이상헌,김민수,정유진,정재학,김소아람,임재영,Howoon Kim 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.9

Undoped ZnO and B-dopoed ZnO (BZO) thin films with 0 to 2.5 at.% B were prepared by usingsol-gel synthesis. Their optical and electrical properties and surface morphology were investigatedusing scanning electron microscopy, photoluminescence (PL), and van der Pauw Hall-effect measurements. All of the thin films were deposited appropriately onto quartz substrates; they exhibiteda fibrous root morphology, with structures that changed in size with increasing B concentration. The PL spectra showed near-band-edge (NBE) emissions and deep-level emissions (DLE). The NBEemission and the DLE for the BZO thin films were more blue-shifted than those for the undopedZnO thin film, and the blue shift increased the efficiency of the NBE emission of the BZO thin films. The Hall-effect data suggested that B doping also improved the electrical properties, such as thecarrier concentration, Hall mobility, and resistivity, of the thin films. The resistivity and the Hallmobility decreased with increasing B concentration and were inversely proportional to the carrierconcentration.

Rare earth (Ce³⁺) activated NaMgF₃ phosphor synthesised by hydrothermal method and its optical properties

Daniel, D. Joseph,Raja, A.,Kim, H.J.,Ramasamy, P. Elsevier 2018 OPTIK -STUTTGART- Vol.158 No.-

<P><B>Abstract</B></P> <P>In this paper, we present an environment friendly hydrothermal process to synthesize nano/sub micro particles of the rare earth activated complex fluoride NaMgF<SUB>3</SUB> at 180 °C. The tittle compound synthesis was carried out at elevated pressure and temperature in an aqueous medium. The powder X-ray diffraction pattern was recorded to check the phase purity of the synthesised compound. Synthesized compounds were micro and nanocrystalline with orthorhombic perovskite crystal structure, space group Pcmn. In order to identify the functional groups Fourier Transform Infrared spectral analysis have been performed. The size and shape of the synthesised compounds were studied by using Field Emission - Scanning Electron Microscope images. Chemical composition of the synthesised compounds were checked by the energy - dispersive X-ray spectra. The absorption bands around 220 and 270 nm were observed which is corresponding to the electronic transition between 4f and 5d configuration of Ce<SUP>3+</SUP>. Photoluminescence emission related to the 5 d → 4 f transitions in Ce<SUP>3+</SUP> was observed at 324 nm. Thermoluminescence properties were studied for the X-ray irradiated samples. The glow curve kinetic parameters of activation energy (E) and frequency factor (S) were calculated using standard methods.</P>

Temperature and magnetic field dependent optical properties of superconducting $MgB_2$ thin film

정종훈,이해자,김경완,김명훈,노태원,강원남,정창욱,이성익,Jung, J. H.,Lee, H. J.,Kim, K. W.,Kim, M. W.,Noh, T. W.,Wang, Y. J.,Kang, W. N.,Jung, C. U.,Lee, Sung-Ik 한국초전도학회 2001 Progress in superconductivity Vol.3 No.1

We investigated the temperature and magnetic field dependent optical properties of a$ MgB_2$ thin film in the far-infrared region. In the superconducting state, i.e. 5 K, we obtained the values of superconducting gap $2\Delta$ ~ 5.2 meV and $2\Delta$ $_{k}$ $B/T_{c}$ ~1.8. Although the value of$ 2\Delta$</TEX$B/T_{c}$ was nearly half of the BCS value, the $2\Delta$ seemed to follow the temperature dependence of the BCS formula. Under the magnetic field (H), the superconducting state became suppressed. Interestingly, we found that the normal state area fraction abruptly increased at low field but slowly increased at high field. It did not follow the H-dependences predicted for a s-wave superconductor (i.e. a linear dependence) nor for a s-wave one (i.e. $H^{1}$2/ dependence). We discussed the complex gap nature of $MgB_2$ in comparison with two gap and anisotropic s-wave scenarios.ios.

Transparent and flexible ultraviolet photoconductors based on solution-processed graphene quantum dots on reduced graphene oxide films

Thanh, Do Trong,Ko, Kang Bok,Khurelbaatar, Zagarzusem,Choi, Chel-Jong,Hong, Chang-Hee,Cuong, Tran Viet Elsevier 2017 Materials research bulletin Vol.91 No.-

<P><B>Abstract</B></P> <P>A combination of graphene quantum dots and chemically reduced graphene oxide films was obtained by spray-coating their dispersions onto an indium tin oxide coated polyethylene terephthalate substrate. Herein, the graphene quantum dots played a major role in the absorption of ultraviolet light and generation of carriers, whereas the reduced graphene films acted as the transparent electron pathway network. Consequently, the fabricated structure showed good transparency and flexibility, and achieved noticeable ultraviolet sensing. The facile, inexpensive, and extremely low temperature techniques used can be easily upgraded to a larger scale and are compatible with other substrates. In addition, a combination of reduced graphene oxide and graphene quantum dots offers a potential graphene-based platform for foldable optoelectronic device applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Solution-processed for fabrication of transparent and flexible ultraviolet sensing. </LI> <LI> Graphene-platform using reduced graphene oxide and graphene quantum dots. </LI> <LI> High transmittance, good flexibility and photoconductor behaviors. </LI> </UL> </P>

Optical properties of PbSe quantum dots doped in borosilicate glass

Chang, J.,Liu, C.,Heo, J. North-Holland 2009 Journal of non-crystalline solids Vol.355 No.37

PbSe quantum dots (QDs) were synthesized in borosilicate glass and their optical properties were investigated. The typical quantum confinement effects were clearly observed from the absorption when the average radii of the QDs changed from 1.7 to 3.1nm. Photoluminescence from PbSe QDs was achieved in 1.1-2.2μm wavelength region that covers the entire fiber-optic telecommunication window. Borosilicate glasses containing controlled size of PbSe QDs provide potentials for the fiber-optic amplifiers.

Multi wall carbon nanotubes assisted synthesis of YVO₄:Eu³⁺ nanocomposites for display device applications

Grandhe, Bhaskar Kumar,Bandi, Vengala Rao,Jang, Kiwan,Ramaprabhu, S.,Lee, Ho-Sueb,Shin, Dong-Soo,Yi, Soung-Soo,Jeong, Jung-Hyun Elsevier 2012 Composites. Part B, Engineering Vol.43 No.3

<P><B>Abstract</B></P> <P>YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites have been synthesized by means of a modified co-precipitation method (CP-CNT). Multi walled carbon nanotubes (MWCNT’s) have been employed in the synthesis of the YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites to enhance its photoluminescence efficiency. The prepared nanocomposites were thoroughly characterized using the characterization techniques namely XRD, SEM, FTIR and Raman scattering. To evaluate the potentiality of the prepared nanocomposites, the same phosphor has also been prepared by using co-precipitation (CP) method without employing multi walled carbon nanotubes and also by means of conventional solid state reaction method (SSR). The photoluminescence spectra of YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites have shown stronger red emission at 619nm (<SUP>5</SUP>D<SUB>0</SUB> → <SUP>7</SUP>F<SUB>2</SUB>) for both the excitation wavelengths (254 and 393nm) than the other two prepared samples. The effect of MWCNT’s on photoluminescent properties of the YVO<SUB>4</SUB>:Eu<SUP>3+</SUP> nanocomposites is also explained.</P>

Upconversion luminescence properties of Er³⁺ in SrLaMgTaO₆ double perovskite phosphor

Kim, D.R.,Park, S.W.,Jeong, J.H.,Choi, H.,Kim, J.H. Pergamon Press 2017 Materials research bulletin Vol.85 No.-

We report the properties of upconversion photoluminescence (UCPL) on SrLaMgTaO<SUB>6</SUB> crystal doped with trivalent erbium at concentrations of 1-20mol% that were synthesized by a solid state reaction method from powder based precursors. The crystal structure, electronic structure, and optical properties of SrLa<SUB>(1-x)</SUB>MgTaO<SUB>6</SUB>:Er<SUB>x</SUB> were discussed by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), UV-vis spectrophotometer, DFT (density functional theory) calculations and photoluminescence (PL) spectra. Under the excitation of a 975nm laser diode, the phosphors emitted green (<SUP>2</SUP>H<SUB>1½</SUB>, <SUP>4</SUP>S<SUB>3/2</SUB>→<SUP>2</SUP>I<SUB>15/2</SUB>) and red (<SUP>4</SUP>F<SUB>9/2</SUB>→<SUP>2</SUP>I<SUB>15/2</SUB>) UCPL. Under the 10mol% concentration of Er<SUP>3+</SUP>, the intensity of the green UCPL had increased in a linearly proportional to Er<SUP>3+</SUP> concentration, which was attributed to the UCPL of low concentration of Er<SUP>3</SUP> and it was mostly generated from ESA process. From higher Er<SUP>3+</SUP>concentration above 10 mol%, however, as the ETU process had additionally participated in UCPL the intensity of UCPL had decreased. It was attributed to the concentration quenching which was more active than ETU process at higher concentration of Er<SUP>3+</SUP> in SrLaMgTaO<SUB>6</SUB>.

Studies on the structural, optical, dielectric and mechanical properties of non-linear optical manganese mercury Tetrathiocyanate glycol mono methyl ether (MMTG) single crystal

A. Bhaskaran,라그하반,R. MohanKumar,R. Jayavel 한국물리학회 2010 Current Applied Physics Vol.10 No.5

Non-linear optical manganese mercury teterathiocyanate glycol monomethyl ether [MnHg(SCN)4(C3H8O2)] compound was synthesized and single crystals were grown from water-glycol monomethyl ether (1:1) mixed solvent by slow cooling method. Structure and crystallinity of the grown crystal were confirmed by both single crystal and powder X-ray diffraction analysis. Presence of functional groups and coordination of glycol monomethyl ether and thiocyanate in MMTG were confirmed by FT-IR analysis. Optical transmittance and second harmonic generation of the grown crystal were studied by UV–Vis spectrum and Kurtz powder technique. A dielectric study was performed on the MMTG single crystal to study the power dissipation of the material in the presence of alternating electric field. Mechanical behaviour was analysed using Vicker’s microhardness test. Optical surface damage measurement was carried out to confirm the suitability of MMTG crystal for NLO applications.

Luminescence properties of Eu²⁺ in T-phase Ba_1.3Ca_0.7SiO₄ lattice from multiple crystallographic sites at different temperatures

Zhang, X.,Meng, F.,Zhang, J.,Cai, P.,Seo, H.J. Elsevier Science Publishers 2016 Materials chemistry and physics Vol.177 No.-

Eu<SUP>2+</SUP>-activated Ba<SUB>1.3</SUB>Ca<SUB>0.7</SUB>SiO<SUB>4</SUB> phosphor has been synthesized by high temperature solid state reaction method. The optical properties of (Ba<SUB>1.29</SUB>Eu<SUB>0.01</SUB>)Ca<SUB>0.7</SUB>SiO<SUB>4</SUB> are investigated using photoluminescence (PL), photoluminescence excitation (PLE) spectra and luminescence decay time measurement between 10 and 523 K. The blue emission band peaking at ~448 nm is observed to be asymmetric. It can be divided into three Gaussian bands with maxima at ~440 (Eu I), ~464 (Eu II) and ~503 nm (Eu III), which is in good agreement with that measured from low temperature at 10 K. The temperature dependence of the PL intensity is also measured. The thermal quenching of Ba<SUB>1.3</SUB>Ca<SUB>0.7</SUB>SiO<SUB>4</SUB>:Eu<SUP>2+</SUP> is about 235 <SUP>o</SUP>C. The PL decay times of 425, 455 and 570 nm emission at 10 K are 0.23, 0.28 and 1.00 μs. They can be attributed to the lifetimes of Eu I, Eu II and Eu III site, respectively. The decay times of the 425 and 455 nm emission almost remain constant at 10 K and 523 K. The decay times of the emission at 570 nm do not change a lot with increasing temperature up to 300 K, then decrease to 0.2 μs at 523 K Ba<SUB>1.3</SUB>Ca<SUB>0.7</SUB>SiO<SUB>4</SUB>:Eu<SUP>2+</SUP> is a candidate blue-emitting phosphor for white LEDs.

Conjugated Polymers Based on Modified Benzo[1,2-b:4,5-b']Dithiophene and Perylene Diimide Derivatives: Good Optical Properties and Tunable Electrochemical Performance

Kun Fang,Xu Ye,Yawen Huang,Guanjun Chang,Junxiao Yang,Yueqin Shen 한국고분자학회 2015 Macromolecular Research Vol.23 No.6

Three original conjugated polymers were devised and synthesized via the alternating conjugated polymerization of the electron-donating monomer of the modified benzo[1,2-b:4,5-b']dithiophene (BDT) and electronaccepting monomers of perylene diimide (PDI), dithienyl-perylene diimide (DTPDI) and dithienocoronene diimide (DTCDI), respectively. The synthesized conjugated polymers presented excellent thermal stability (Td >400 oC) as well as broad absorption in visible region and narrow gap of energy level (1.80 to 2.01 eV). Moreover, P(BDT-DTCDI) exhibited strong fluorescence properties ( =736 nm with excitation at 680 nm). According to the theoretical calculations, P(BDT-PDI) and P(BDT-DTPDI) displayed significant polymer backbone torsion (41.44o and 39.64o), and P(BDT-DTCDI) had highly coplanar backbone with negligible angle between BDT and DTCDI. The results indicated that P(BDT-DTCDI) had potential applications in the fields of organic thin-film transistors (OTFTs) and fluorescence materials, and P(BDT-PDI) and P(BDT-DTPDI) could be used as a stable n-type semiconductor for polymer solar cells.