Laser-induced Doping of Aluminum into a Cadmium Telluride Thin Film: Electrical and Optical Properties

김남훈,Kuk Do Myung,조금배,이우선 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.3

The electrical properties of cadmium telluride (CdTe) thin films are essentially determined by the doping process; the laser-induced doping method was chosen to dope aluminum (Al) as a donor into CdTe thin films to perform a selective and controllable doping process for multilayer structured photovoltaic devices. The laser-induced doping of Al used a helium-neon (He-Ne) laser (632.8 nm)to expose sputtering-deposited p-type CdTe thin films after they had been annealed at 400 C for 1 hour. The Auger electron spectroscopy depth profile showed better doping uniformity for longer exposure to the time of He-Ne laser in the doping process. The conductivity of the CdTe thin films was changed from p-type to n-type once the doping of Al was performed. The optical band gap energy of the CdTe thin films decreased from 1.451 eV to 1.418 eV after 10 minutes of Al doping. The average absorbance value of the CdTe thin films improved from 1.58 to 1.72 by doping with Al due to impurity-scattering via the doped Al atoms in the CdTe thin films. The resistivity of the Al-doped CdTe thin films was reduced significantly from the order of 104 -cm to the order of 10.6 -cm after only 1 minute of exposure. The carrier concentration of the CdTe thin films increased to a maximum value of 1.2 × 1021 cm.3 after a 10-minute exposure to the He-Ne laser. The laser-induced doping of Al into CdTe thin films is a very simple and effective method to dope a multilayered thin-film solar cell with a relatively short process time, no wet-process, and selective treatment to control the conductivity type, the optical band gap energy, the absorbance, the carrier concentration, and resistivity of the thin films. The electrical properties of cadmium telluride (CdTe) thin films are essentially determined by the doping process; the laser-induced doping method was chosen to dope aluminum (Al) as a donor into CdTe thin films to perform a selective and controllable doping process for multilayer structured photovoltaic devices. The laser-induced doping of Al used a helium-neon (He-Ne) laser (632.8 nm)to expose sputtering-deposited p-type CdTe thin films after they had been annealed at 400 C for 1 hour. The Auger electron spectroscopy depth profile showed better doping uniformity for longer exposure to the time of He-Ne laser in the doping process. The conductivity of the CdTe thin films was changed from p-type to n-type once the doping of Al was performed. The optical band gap energy of the CdTe thin films decreased from 1.451 eV to 1.418 eV after 10 minutes of Al doping. The average absorbance value of the CdTe thin films improved from 1.58 to 1.72 by doping with Al due to impurity-scattering via the doped Al atoms in the CdTe thin films. The resistivity of the Al-doped CdTe thin films was reduced significantly from the order of 104 -cm to the order of 10.6 -cm after only 1 minute of exposure. The carrier concentration of the CdTe thin films increased to a maximum value of 1.2 × 1021 cm.3 after a 10-minute exposure to the He-Ne laser. The laser-induced doping of Al into CdTe thin films is a very simple and effective method to dope a multilayered thin-film solar cell with a relatively short process time, no wet-process, and selective treatment to control the conductivity type, the optical band gap energy, the absorbance, the carrier concentration, and resistivity of the thin films.

알루미늄이 첨가된 Li(Ni_1/3Co_1/3Mn_1/3-xAl_x)O₂ 양극활물질의 전기화학적 특성

김선혜,심광보,김창삼,Kim Seon-Hye,Shim Kwang-Bo,Kim Chang-Sam 한국전기화학회 2006 한국전기화학회지 Vol.9 No.2

초음파분무열분해법과 한 단계의 후열처리로 이차상이 없는 Al이 첨가된 $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01. 0.05) 리튬이차전지용 양극활물질을 합성하였다. 합성된 분말은 Al의 첨가량이 많아짐에 따라서 $I_{003}/I_{104}$ 비는 감소하고 입자가 커지는 경향을 보였다. 상온에서 전류밀도 1C의 rate로 $3.0\sim4.5V$ 범위에서 충방전 시험한 결과, Al 치환량이 0.5와 1.0 at%에서는 초기용량이 180과 $184mAhg^{-1}$으로 치환하지 않았을 때의 $182mAhg^{-1}$과 차이가 없었으며, 싸이클 특성도 치환하지 않은 것과 0.5, 1.0 at% 치환한 조성에서 각각 81, 77, 81%의 방전용량이 유지되었다. 그러나 $3.0\sim4.6V$에서는 치환효과가 확실하게 나타나서, 50 싸이클 후의 치환하지 않은 것의 방전용량은 초기용량의 30%가지 감소한데 비하여 Al을 0.5 at% 치환한 것은 70%를 유지하였다. 치환에 의한 싸이클 특성 향상은 XPS 분석 결과 Al 치환이 $Mn^{3+}$의 양을 감소시켰기 때문인 것으로 사료되었다. Cathode materials of Al-doped $Li(Ni_{1/3}Co_{1/3}Mn_{1/3-x}Al_x)O_2$ (x=0.0, 0.005, 0.01 0.05) for lithium ion batteries were synthesized with ultra-sonic spray pyrolysis method and single-step heat treatment. No secondary phases were found in all synthesized powders. The intensity ratio of $I_{003}\;to\;I_{104}$, however, slightly decreased and the particle size increased with the Al contents. The cells with bare, 0.5 and 1.0 at% Al-doped powders showed the initial discharge capacities of 182, 180 and $184mAhg^{-1}$ in a voltage range of $3.0\sim4.5V$ at 1C rate, and the capacity retentions of 81, 77 and 78% at the end of 30 cycles, respectively. But in the voltage range of $3.0\sim4.6V$, the Al-doping significantly enhanced the cycle stability. For example, the discharge capacity after 50 cycles was maintained to 70% in the 0.5 at% Al-doped sample compared to only 30% in no doped sample. The improvement of the cycle stability was thought to be due to $Mn^{3+}$ ion decrease as the Al doping from the XPS analysis results.

Al이 도핑된 GaInAsSb/GaSb의 경계면에서의 밴드정렬

심규리,Shim, Kyurhee 한국결정성장학회 2016 韓國結晶成長學會誌 Vol.26 No.6

GaSb 기판위에 Al이 도핑된 GaInAsSb(Al-GaInAsSb)에 대한 최고 가전대 준위(VBM)와 최저 전도대 준위(CBM) 변화를 범용적 밀접결합방법에 근거한 해석적 근사법을 이용하여 계산하였다. GaSb와 Al-GaInAsSb 의 상대적 VBM과 CBM 준위에 따라 경계면에서의 밴드정렬 타입과 가전자대 오프셋(VBO)과 전도대 오프셋(CBO)이 결정된다. 본 논문에서는 Al 도핑이 GaInAsSb의 양이온 자리에 치환된다는 가정하에 이론이 전개 되었으며, Al은 부식등으로 결정의 질을 떨어트릴 수 있는 요인이 되므로 20 %까지 제한하였다. Al 도핑 결과, 전 구간에서 제 II 형의 밴드정렬형태를 갖게 되며, 밴드갭이 증가되는 반면 VBO와 CBO 는 감소됨을 알수 있었다. CBO 에 대한 감소비율 VBO 보다 더 크므로, Al 도핑은 경계면에서의 전자 콘트롤에 더 효율적으로 작용함을 알 수 있었다. Al-GaInAsSb은 전 구간에서 $E({\Gamma})$가 E(L)이나 E(X)보다 낮은 직접 갭을 나타 내고 있지만, Sb 성분이 많아지면(70~80 % 이상) E(L)과 E(X)이 $E({\Gamma})$에 가까워져서 전자 이동도에 영향을 주어 광학적 효율이 다소 떨어질 수 있음을 알 수 있었다. The valence band maximum (VBM) and conduction band minimum (CBM) of Al-doped GaInAsSb alloys substrated on GaSb are calculated by using an analytic approximation based on the tight binding method. The relative positions of the VBM and CBM between Al-GaInASSb and GaSb determine band alignement type, valence band offset (VBO) and conductin band offset (CBO) for the heterojunctions. In this study, aluminium doping is assumed to be substituted in the cation site and limited up to 20 % because it can easily oxidize and degrade materials. It is found that the Al-doped alloys exhibit type-II band alignments over the entire composition range and make the band gaps increase, whereas the VBO and CBO decrease. The decreasing rate of VBO is higher than that of CBO, which implies the Al components play a decisive role in controlling electrons at the interface. The Al-dopled GaInAsSb alloy has a direct band gap induced by $E({\Gamma})$ with a considerable distance from the E(L) and E(X), however, $E({\Gamma})$ approaches to E(L) and E(X) in the high Sb concentration (Sb > 0.7-0.8) which might affect the electron mobility and degrade the optical quality.

AuGe 상에 성장된 ZnO:Al 나노막대의 구조적, 광학적, 전기적 특성 평가

김시내,정미나,오승준,이원재,구지은,허인혜,안형수,이삼녕,장지호,정희정,이병우,황현희 한국물리학회 2008 새물리 Vol.57 No.3

The structural, optical, and electrical properties of ZnO:Al nanorods with different Al contents were investigated. The ZnO:Al nanorods were synthesized using a AuGe catalyst at a growth temperature of 600 $^\circ$C under an Ar gas flow of 600 sccm by changing the mixed-source weight ratio (Zn and Al powers) in a horizontal tube furnace. ZnO nanorods grown at 600 $^\circ$C under a carrier gas flour of 600 sccm showed a density of 17.125 ea/$\mu$m$^2$ and a uniform diameter of 50$\pm$10 nm with a $\pm$5 degree dispersion angle in a direction normal to the substrate. A strong UV emission was observed art 3.24 eV with a high relative emission ratio and a narrow FWHM (full width at half maximum), which indicated that the samples had high crystallinity. From the PL measurement, the peak position of the near-band-edge (NBE) emission of the ZnO:Al nanorods was shifted by $\sim$17 meV in the high-energy direction, which indicated an increase in the free carrier concentration due to Al doping in the ZnO nanorods. Also, the carrier concentration of the ZnO:Al nanorods (doped at 1 at.\%) was confirmed to be 1.09 $\times$ 10$^{21}$ cm$^{-3}$ by hall measurements at room temperature. ZnO:Al 나노막대의 Al 조성에 따른 구조적, 광학적, 전기적 특성의 변화를 고찰하였다. ZnO:Al 나노막대는 수평형 열 산화로에서 AuGe 촉매를 이용하고 캐리어 가스인 Ar 가스 분위기하에서 Zn와 Al의 혼합 분말을 사용하여 합성되었다. AuGe 촉매 유무에 따른 나노막대의 형상 변화를 관찰하여 AuGe의 역할을 고찰하였고, ZnO 나노막대의 성장 조건 ($T_G$: 550 $\sim$ 700 $^\circ$C, Ar gas flow: 200 $\sim$ 1000 sccm)을 최적화 시켰다. 600 $^\circ$C, 600 sccm에서 성장된 ZnO 나노막대는 17.125 ea/$\mu$m$^2$의 밀도와, 50$\pm$10 nm 균일한 직경이 관찰되었고, 기판 면 방향에서 $\pm$5 degree의 분산각을 가짐을 확인하였다. 또한 실온에서 발광특성 평가를 통해서 3.24 eV의 강한 UV 발광과 좁은 반치폭으로 양호한 결정성을 가지고 있다고 판단하였다. 반면 Al 도핑된 ZnO:Al 나노막대에서는, Al 도핑에 의해서 ZnO 나노막대의 형상 변화가 관찰되었으며, 발광 특성 평가에서 높은 에너지 쪽으로의 밴드 단의 피크 위치 변화를 통해, Al 농도 증가에 따른 나노막대 내부의 전하농도의 증가가 예상되었다. 이러한 예상은 실온에서 홀 측정을 통하여 확인하였으며, 가장 높은 Al 농도를 갖는 시료에서 고농도 ($<$1.09 $\times$ 10$^{21}$ cm$^{-3}$) 전하농도가 확인되었다.

졸-겔법으로 제조한 Al-doped ZnO 박막의 특성에 관한 연구

김용남,이승수,송준광,노태민,김정우,이희수,Kim, Yong-Nam,Lee, Seoung-Soo,Song, Jun-Kwang,Noh, Tai-Min,Kim, Jung-Woo,Lee, Hee-Soo 한국결정성장학회 2008 韓國結晶成長學會誌 Vol.18 No.1

졸-겔 공정을 이용하여 유리기판 위에 Al-doped ZnO(AZO) 박막을 제조하였고, AZO 박막의 특성에 대하여 Al 전구체 종류 및 post-annealing 온도가 미치는 영향에 대하여 고찰하였다. AZO 박막 제조용 졸은 zinc acetate, EtOH, MEA 등을 사용하여 제조하였고, Al doping 을 위한 전구체로는 aluminum nitrate 와 aluminum chloride 를 사용하였다. Sol 내의 Zn 농도는 0.5 mol/l 로 하였고, Al doping 양은 Zn 대비 1 at%로 고정하였다. 유리기판 위에 졸을 spin-coating 한 후 $550^{\circ}C$에서 2 시간 동안 열처리한 후, $N_2$와 $H_2$의 비가 9 : 1인 환원 분위기 내에서 $300^{\circ}C,\;400^{\circ}C,\;500^{\circ}C$인 온도에서 2시간 동안 post-annealing을 진행하였다. 제조된 AZO 박막의 구조적, 전기적, 광학적 특성은 XRD, FE-SEM, AFM, Hall effect measurement system 및 UV-Visible spectroscopy를 이용하여 분석하였다. Al 전구체로서 aluminum nitrate 를 사용한 경우가 aluminum chloride 를 사용하여 제조한 AZO 박막보다 우수한 광학적, 전기적 특성을 나타내었으며, post-annealing 온도가 증가함에 따라 비저항과 투과율은 감소하였다. $500^{\circ}C$에서 post-annealing한 AZO 박막의 전기비저항 값은 $2{\times}10^{-3}{\Omega}{\cdot}cm$이었고, 투과율은 $300^{\circ}C$에서 91%로 가장 높게 나타났다. AI-doped ZnO(AZO) thin films have been fabricated on glass substrate by sol-gel method, and the effect of Al precursors and post-annealing temperature on the characteristics of AZO thin films was investigated. The sol was prepared with zinc acetate, EtOH, MEA and Al precursors. In order to dope Al in ZnO, two types of aluminum nitrate and aluminum chloride were used as Al precursor. Zinc concentration was 0.5 mol/l and the content of Al precursor was 1 at% of Zn in the sol. The sol was spin-coated on glass substrate, and the coated films were annealed at 550ue for 2 hand were post-annealed at temperature ranges of $300{\sim}500^{\circ}C$ for 2 h in reducing atmosphere ($N_2/H_2$= 9/1). Structural, electrical and optical propertis of the fabricated AZO thin films were analyzed by XRD, FE-SEM, AFM, hall effect measurement system and UV-visible spectroscopy. Optical and electrical properties of AZO thin films prepared with aluminum nitrate as Al precursor were better than those of films prepared with aluminum chloride. The electrical resistivity and the optical transmittance of films decreased with increasing post-annealing temperatures. The minimum electrical resistivity of $2{\times}10^{-3}$ and the maximum optical transmittance of 91% were obtained for the AZO thin films post-annealed at $550^{\circ}C\;and\;300^{\circ}C$, respectively.

Li+ 및 Al3+ 이온의 첨가에 의한 YPO4:Eu3+ 형광체의 형광특성 비교

신평지,이성수 한국물리학회 2013 새물리 Vol.63 No.7

Li and Al were doped as sensitizers to improve the luminescent brightness, and the conventional solid-state reaction method was used to synthesize phosphors. The effects of Li and Al doping on the microstructures of YPO4:Eu3+ phosphors were measured by Using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The luminescent characteristics were characterized by using photoluminescence (PL) and photoluminescence excitation (PLE) measurements. In addition, the dependences of the various optical and morphological properties of the prepared materials on the Li/Al concentration are discussed. Incorporation of Li+/Al3+ ions into the YPO4:Eu phosphors greatly enhanced the crystallinity, the particle size and, hence, the luminescence properties, and the optimum concentration in the cases of both the Li and the Al dopants were found to be 10 mol%. The improvement in the photoluminescence performance with Li/Al doping may result from the improved crystallinity and from the enlarged grain sizes which lower the scattering loss and the distortion of symmetry. Li+와 Al3+을 증감제로 이용하여 Eu3+가 첨가된 YPO4적색 형광체를 고상반응법 (solid state reaction)을 이용하여제조하였다. 400℃에서 10시간 하소하였고, 1200℃에서3시간 소결하였다. Li+와 Al3+의 농도변화에 따른YPO4:Eu3+ 형광체의 결정성의 변화를 X-ray diffraction (XRD)을이용하여 조사하였고 전자주사현미경 (field emission scanning electron microscopy, FESEM)으로 분말의 표면 형상을 분석하였다. 형광광도계를이용하여 여기발광스펙트럼 및 발광스펙트럼 등의 형광특성을조사하였다. 그 결과 YPO4:Eu3+ 형광체에 Li+/Al3+를첨가하였을 때 순수 YPO4:Eu3+형광체일 때 보다 형광체 분말의결정성이 향상되고 그레인 사이즈가 커짐을 알 수 있으며, 형광세기가증가함을 알 수 있다. 이것은 형광체 분말의 크기가 커짐에 따라경계밀도가 적어짐으로 경계에서의 산란에 의한 빛의 손실이 줄어들기때문인 것으로 생각할 수 있다.

Sensitivity enhancement of AZO-based ethanol sensor decorated by Au nano-islands

H. Farajollahi,Z. Golshan Bafghi,E. Mohammadi,N. Manavizadeh,A. Salehi 한국물리학회 2020 Current Applied Physics Vol.20 No.8

Detecting the hazardous gases for monitoring air pollution and medical diagnosis make highly sensitive gas sensors appeal to many researches. In this paper, benefiting from unique properties of noble metals, Al-doped ZnO based Ethanol sensors were fabricated and characterized in three structures including Al: ZnO thin film, Silver and Gold nano-islands on Al: ZnO thin film. The Silver and Gold thin films turn to nano-islands after a simple annealing process. The XRD analysis of the sputtered Al: ZnO layer indicates the wurtzite crystal structure of the layer with a peak at (002) plane. Moreover, the sensitivity study reveals that Nano-islands of noble metals substantially affects the sensitivity of the sensors. The decorated Gold nano-island Al: ZnO Ethanol sensor has the highest response showing an amount of 45. The response of Al: ZnO and Silver decorated Al: ZnO sensors are virtually identical to all concentrations of Ethanol, whereas the Al: ZnO gas sensor with Gold nano-islands has the substantial sensitivity for different concentrations. In addition, the response times of the sensors are 85, 70 and 90 s for Al: ZnO, Al: ZnO with Ag islands and Al: ZnO decorated by Au islands, respectively. The recovery time of Al: ZnO sensor decorated by Au islands is about 23s, while the recovery time of the Al: ZnO and Al: ZnO decorated by Silver islands are 360 and 370s, respectively. Hence, the simple annealing process on the sputtered gas sensor with a thin layer of Gold makes nano-islands on the sensor which elevates the performance of Ethanol sensing due to the high sensitivity and sensitivity of the sensor.

First-principles study on the doping effects of Al in a-MnO2

Zhenhua Yang,Xianyou Wang,Yunqing Huang 한국물리학회 2015 Current Applied Physics Vol.15 No.11

In this paper, first-principles calculations have been implemented to study the structural relaxation, formation energies and electronic structure of Al doped a-MnO2. Both Al insertion and Al substitution reactions in the a-MnO2 were considered. Calculated formation energies indicate that Mn atom is easier to be displaced by Al atom under the O-rich growth condition compared with Al insertion reaction. Besides, it can be found that Al doping can afford acceptor impurity level which can accommodate electrons, thus contributing to the improvement of conductivity of a-MnO2. The conductivity of a-MnO2 is gradually improved with the increasing doping concentration of Al, and Al0.0417Mn0.9583O2 exhibits the best conductivity. Lastly, the electronic structure of Al0.0417Mn0.9583O2 was further investigated by analysis of total charge density and Bader charge. It is clear that Al doping can afford more electrons for a-MnO2, which also contributes to improvement of its conductivity.

Microstructure and property evolution of diamond-like carbon films co-doped by Al and Ti with different ratios

Zhou, Yong,Guo, Peng,Sun, Lili,Liu, Linlin,Xu, Xiaowei,Li, Wenxian,Li, Xiaowei,Lee, Kwang-Ryeol,Wang, Aiying Elsevier Sequoia 2019 Surface & coatings technology Vol.361 No.-

<P><B>Abstract</B></P> <P>Diamond-like carbon (DLC) films with weak carbide metal Al and carbide metal Ti co-doping (Al/Ti-DLC) were prepared by a hybrid ion beam deposition system. The atomic ratios of doped Al to Ti were tailored via designing the special Al/Ti combined sputtering target. The composition, microstructure, roughness, residual stress, hardness, toughness, and tribological behaviors of the deposited films were systematically evaluated to explore the dependence of structural properties on Al/Ti ratios. Results indicated that the high-throughput preparation of DLC films with different Al/Ti atomic ratios was achieved by tailoring the sputtering target and process parameters without the difference in both the film thickness and total Al/Ti content. With the Al/Ti ratios in the films decreased from 8.8 to 3.0, the residual stress, hardness, and toughness of Al/Ti-DLC films increased obviously, originating from the increased fraction of titanium carbide and the reduced Al content. However, the coefficient of friction and wear rate with decreasing the Al/Ti ratio were obviously improved, which was related with the transformation of underlying friction mechanism from the sliding interface graphitization to dangling bond-passivation. The present results not only suggest a high-throughput method to fabricate co-doped DLC films, but also promote the scientific understanding and engineering application of DLC films with high performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti/Al co-doped diamond-like carbon films were fabricated by a hybrid ion beam method. </LI> <LI> Different Al/Ti ratios were successfully achieved at one time using designed target. </LI> <LI> Al/Ti ratios had no effect on the chemical state of co-doped Ti and Al atoms. </LI> <LI> The mechanical and tribological properties were strongly dependent on Ti/Al ratios. </LI> <LI> Different friction mechanisms were observed with Al/Ti ratios ranged from 8.8 to 3.0. </LI> </UL> </P>

급속 열처리 방법에 의한 Al-doped Zinc Oxide (AZO) Films의 제조 및 특성 평가

김성진,최균,최세영,Kim, Sung-Jin,Choi, Kyoon,Choi, Se-Young 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.7

In this study, transparent conducting Al-doped Zinc Oxide (AZO) films with a thickness of 150 nm were prepared on corning glass substrate by the RF magnetron sputtering with using a Al-doped zinc oxide (AZO), ($Al_2O_3$: 2 wt%) target at room temperature. This study investigated the effect of rapid thermal annealing temperature and oxygen ambient on structural, electrical and optical properties of Al-doped zinc oxide (AZO) thin films. The films were annealed at temperatures ranging from 400 to $700^{\circ}C$ by using Rapid thermal equipment in oxygen ambient. The effect of RTA treatment on the structural properties were studied by x-ray diffraction and atomic force microscopy. It is observed that the Al-doped zinc oxide (AZO) thin film annealed at $500^{\circ}C$ at 5 minute oxygen ambient gas reveals the strongest XRD emission intensity and narrowest full width at half maximum among the temperature studied. The enhanced UV emission from the film annealed at $500^{\circ}C$ at 5 minute oxygen ambient gas is attributed to the improved crystalline quality of Al-doped zinc oxide (AZO) thin film due to the effective relaxation of residual compressive stress and achieving maximum grain size.