Nonvolatile memories using deep traps formed in HfO₂ by Nb ion implantation

We report nonvolatile memories (NVMs) based on deep-energy trap levels formed in HfO₂ by metal ion implantation. A comparison of Nb- and Ta-implanted samples shows that suitable charge-trapping centers are formed in Nb-implanted samples, but not in Ta-implanted samples. This is consistent with density-functional theory calculations which predict that only Nb will form deep-energy levels in the bandgap of HfO₂. Photocurrent spectroscopy exhibits characteristics consistent with one of the trap levels predicted in these calculations. Nb-implanted samples showing memory windows in capacitance–voltage (V) curves always exhibit current (I) peaks in I–V curves, indicating that NVM effects result from deep traps in HfO₂. In contrast, Ta-implanted samples show dielectric breakdowns during the I–V sweeps between 5 and 11 V, consistent with the fact that no trap levels are present. For a sample implanted with a fluence of 10¹³Nb cm⁻², the charge losses after 10⁴ s are ∼9.8 and ∼25.5% at room temperature (RT) and 85°C, respectively, and the expected charge loss after 10 years is ∼34% at RT, very promising for commercial NVMs

The Spitzer C2D Survey of Nearby Dense Cores: Jet and Molecular Outflow Associated With A Young Stellar Object in Core A of L1251

A long infrared jet has been discovered by the Spitzer c2d Legacy Program in core A of L1251. It is associated with a very embedded Class 0 object with an accretion luminosity of about 0.9 L(circle dot) derived by radiative transfer model fitting to the observed spectral energy distribution. Comparing the observed Infrared Array Camera colors along the infrared jet with those calculated from a model of an admixture of gas with a power-law temperature distribution indicates that the jet is possibly created by a paraboloidal bow shock propagating into the ambient medium of n(H(2)) = 10(5) cm(-3). In addition, the variation of the power-law index along the jet suggests that the portion of hot gas decreases with distance from the jet engine. The molecular outflow in this region has been mapped for the first time using CO data. From the calculated outflow momentum flux, a very strong lower limit to the average accretion luminosity is 3.6 sin i/cos(3) i L(circle dot), indicative of a decrease in the accretion rate with time.Korean government (MEST) 2009-0062865NRF R01-2007-000-20336-0NASA 1407, 1224608Astronom

Strong enhancement of ultraviolet emission from ZnO films by V implantation

ZnOfilms were prepared on Si(100) wafers by rf sputtering and subsequently implanted with V ions to fluences of (1,2.5,5,10)×10¹⁵ cm¯². The room-temperature ultraviolet photoluminescence(PL) intensity of the implantedfilms is shown to increase with increasing fluence up to 2.5×1015 cm−2, becoming ∼37 times more intense than the emission from the unimplanted ZnOfilm, before decreasing at higher fluences. The increase in PL intensity is correlated with improved crystallinity of ZnO, accompanied by a reduction in the concentration of deep-level native defects by V incorporation into the ZnO lattice, as verified by x-ray diffraction, x-ray photoelectron spectroscopy, and low-temperature PL. The subsequent reduction in PL intensity at fluences higher than 2.5×10¹⁵ cm¯² is shown to result from the deterioration of the crystal quality and the precipitation of V secondary phase possibly introducing defects in the films

Aerobic training with rhythmic functional movement: Influence on cardiopulmonary function, functional movement and Quality of life in the elderly women

The purpose of this study was to investigate the effects of rhythm of aerobic exercise in elderly women. Thirty subjects were randomly divided into two groups: The aerobic exercise with rhythm (experimental group, n=9) and aerobic exercise without rhythm (control group, n=10). All subjects performed aerobic exercise composed of functional movements. During the exercise, control group subjects were performed the functional movement exercise only to the beat without music or rhythm and experimental group subjects were performed the functional movement exercise to the rhythm of the music. All subjects performed exercise for 50 minutes, twice a week, total of 8 weeks. The forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and maximal voluntary ventilation (MVV) were measured. Functional movements were assessed using FMS (Functional Movement Screen). Quality of life (QOL) were assessed using SF-36. Evaluation was performed before and after 8 weeks of exercise and one month later for follow-up. The FVV, FVC1, MVV, FMS, and SF-36 have shown a significant difference in time as a result of the two-way repeated-measures analysis. The post mean change of FVC1, MVV, FMS, and SF-36 were significantly different between groups. In this study, aerobic exercise, which is composed of rhythmic functional movement, helped improve functional movement and QOL for the elderly women. When the experimental group and the control group were compared, the improvement of the experimental group with music and rhythm was more positive than the exercise using the same functional movement.This research was supported by the Daejeon University fund (2017)

Effect of (O, As) dual implantation on p-type doping of ZnO films

Optical and electrical characteristics of ZnOfilms co-implanted with O and As ions have been investigated by photoluminescence(PL), Hall-effect, and current-voltage (I-V) measurements. 100-nm-thick ZnOfilms grown on n-type Si (100) wafers by RF sputtering have been implanted with various fluences of 30 keV O and 100 keV As ions at room temperature, and subsequently annealed at 800 °C for 20 min in a N2 ambient. The dually-implanted ZnOfilms show stable p-type characteristics for particular implant combinations, consistent with the observation of dominant PL peaks at 3.328 and 3.357 eV that are associated with the acceptor levels. For these dually-implanted p-type ZnO films/n-type Si diodes, the I-V curves show rectifying p-n junction behavior. Other singly (As)- or dually-implanted samples show n-type or indeterminable doping characteristics. These results suggest that O implantation plays a key role in forming p-type ZnOfilms by reducing the oxygen vacancy concentration and facilitating the formation of As-related acceptors in ZnO.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2011-0017373)

Simple Structured DPP-based Small Molecules for High Efficient Organic Photovoltaics

OAIID:oai:osos.snu.ac.kr:snu2013-01/104/0000001236/8SEQ:8PERF_CD:SNU2013-01EVAL_ITEM_CD:104USER_ID:0000001236ADJUST_YN:NEMP_ID:A004558DEPT_CD:445CITE_RATE:0FILENAME:이종원.pdfDEPT_NM:재료공학부EMAIL:[email protected]:

Formation characteristics and photoluminescence of Ge nanocrystals in HfO[sub 2]

Genanocrystals (NCs) are shown to form within HfO₂ at relatively low annealing temperatures (600–700 °C) and to exhibit characteristic photoluminescence(PL) emission consistent with quantum confinement effects. After annealing at 600 °C, sample implanted with 8.4×10¹⁵ Ge cm⁻² show two major PL peaks, at 0.94 and 0.88 eV, which are attributed to no-phonon and transverse-optical phonon replica of Ge NCs, respectively. The intensity reaches a maximum for annealing temperatures around 700 °C and decreases at higher temperatures as the NC size continues to increase. The no-phonon emission also undergoes a significant redshift for temperatures above 800 °C. For fluences in the range from 8.4×1015 to 2.5×10¹⁶ cm⁻², the average NC size increases from ∼13.5±2.6 to ∼20.0±3.7 nm. These NC sizes are much larger than within amorphous SiO₂. Implanted Ge is shown to form Ge NCs within the matrix of monoclinic (m)-HfO₂ during thermal annealing with the orientation relationship of [101]m-HfO₂//[110]Ge NC.S.H.C. and R.G.E. acknowledge supports from the Korea Research Foundation Grant Grant No. KRF-2007-521- C00094 and from the Australian Research Council Discovery Project, respectively