Low-temperature synthesis of graphene by chemical vapor deposition and its applications

Son, Myungwoo,Ham, Moon-Ho Elsevier 2017 Flatchem Vol.5 No.-

<P><B>Abstract</B></P> <P>Graphene is currently one of the most advanced materials under study for the development of a wide range of future device applications, owing to fascinating properties such as high carrier mobility, high electrical conductivity, as well as excellent mechanical flexibility and strength. A key requirement for the practical applications of graphene is the synthesis of large-area, high-quality films at low temperature, especially below 400°C, which would enable the direct integration of graphene into the manufacturing technologies of complementary metal-oxide semiconductor (CMOS) or flexible devices. Chemical vapor deposition (CVD), a well-known and controllable method to prepare thin films, has attracted significant attention for the synthesis of large-area, uniform graphene samples. Nonetheless, significant efforts are still needed to improve our fundamental understanding of the graphene growth mechanism; a better understanding would enable reducing the growth temperature and optimizing the engineering parameters for the fabrication of new electronic devices. This article reviews recent progress in the low-temperature synthesis of graphene by CVD, with a special focus on the key technical factors that can be controlled to drastically reduce the synthesis temperature. Furthermore, the applications of graphene grown by low-temperature CVD are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Recent progress in low-temperature synthesis of graphene is presented. </LI> <LI> Graphene synthesized by chemical vapor deposition is discussed. </LI> <LI> The key technical parameters for low-temperature synthesis of graphene are discussed. </LI> <LI> The applications of low-temperature-grown graphene are discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Extra-Low Temperature Growth of ZnO Thin Films by Atomic Layer Deposition

E. Guziewicz,M. Godlewski,K. Kopalko,I. A. Kowalik,S. Yatsunenko,V. Osinnyi,W. Paszkowicz,E. Lusakowska,P. D luzewski 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

We report on ZnO thin films grown by the atomic layer deposition method at temperature of 200 ℃ and below. Low-temperature ZnO layers show bright excitonic photoluminescence for “asgrown” samples. Defect-related bands usually observed in the green and the red regions are of low intensity and are absent for ZnO layers grown at 140 ℃ − 200 ℃, which is evidence that competing radiative decay channels are ineffective. We relate this to a blocking of the vacancy formation, which is thermally suppressed at low growth temperature. Hall measurements show that the free-carrier concentration strongly depends on the growth temperature and has the lowest value of 2 · 1017 /cm3 for films grown at 100 ℃ and below. We report on ZnO thin films grown by the atomic layer deposition method at temperature of 200 ℃ and below. Low-temperature ZnO layers show bright excitonic photoluminescence for “asgrown” samples. Defect-related bands usually observed in the green and the red regions are of low intensity and are absent for ZnO layers grown at 140 ℃ − 200 ℃, which is evidence that competing radiative decay channels are ineffective. We relate this to a blocking of the vacancy formation, which is thermally suppressed at low growth temperature. Hall measurements show that the free-carrier concentration strongly depends on the growth temperature and has the lowest value of 2 · 1017 /cm3 for films grown at 100 ℃ and below.

Low-temperature deposition of nanocrystalline Al₂O₃ films by ion source-assisted magnetron sputtering

Ding, Ji Cheng,Zhang, Teng Fei,Mane, Rajaram S.,Kim, Kwang-Ho,Kang, Myung Chang,Zou, Chang Wei,Wang, Qi Min Elsevier 2018 Vacuum Vol.149 No.-

<P><B>Abstract</B></P> <P>In this paper, bipolar pulse reactive magnetron sputtering with ion source assisted deposition method has been utilized for the deposition of nanocrystalline alumina (Al<SUB>2</SUB>O<SUB>3</SUB>) films at the temperature of 300 °C onto silicon (111) wafers, and cemented carbide substrates. The influence of ion source power, i.e. 0, 1.0, 1.5 and 2.0 kW on the structure, morphology, compressive stress and mechanical properties of the Al<SUB>2</SUB>O<SUB>3</SUB> films were investigated. In absence of ion source power assistance, an amorphous Al<SUB>2</SUB>O<SUB>3</SUB> film was dominant at deposition temperature of 300 °C. With ion source assisted deposition, the crystalline γ-Al<SUB>2</SUB>O<SUB>3</SUB> films were obtained at the same conditions, suggesting an importance of ion source power in crystallinity development of metal oxide films obtained from magnetron sputtering deposition method. Images of surface morphology clearly demonstrated the difference in granular sizes of film surfaces prepared with and without ion source powers. With increasing ion source power from 1.0 to 2.0 kW, the micro-hardness and compressive stress of the films were increased from 7 GPa to 13 GPa and 0.3 GPa to 1.1 GPa, respectively. Results revealed that the reactive magnetron sputtering with the ion source assisted deposition was a simple and effective way to prepare nanocrystalline γ-Al<SUB>2</SUB>O<SUB>3</SUB> films at low temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al<SUB>2</SUB>O<SUB>3</SUB> films were synthesized by Ar ion source-assisted bipolar pulsed sputtering technique. </LI> <LI> Nanocrystalline Al<SUB>2</SUB>O<SUB>3</SUB> films were obtained at relatively low deposition temperature (300 °C) and low bias voltage conditions. </LI> <LI> The orientation and microstructure of the films can be adjusted by altering the ion source power. </LI> <LI> The synthesis approach of crystalline Al<SUB>2</SUB>O<SUB>3</SUB> films in this study is promising for large-scale industrial applications. </LI> </UL> </P>

Low-Temperature Atomic Layer Deposition of Highly Conformal Tin Nitride Thin Films for Energy Storage Devices

Ansari, Mohd Zahid,Nandi, Dip K.,Janicek, Petr,Ansari, Sajid Ali,Ramesh, Rahul,Cheon, Taehoon,Shong, Bonggeun,Kim, Soo-Hyun American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.46

<P>We present an atomic layer deposition (ALD) process for the synthesis of tin nitride (SnN<SUB><I>x</I></SUB>) thin films using tetrakis(dimethylamino) tin (TDMASn, Sn(NMe<SUB>2</SUB>)<SUB>4</SUB>) and ammonia (NH<SUB>3</SUB>) as the precursors at low deposition temperatures (70-200 °C). This newly developed ALD scheme exhibits ideal ALD features such as self-limited film growth at 150 °C. The growth per cycle (GPC) was found to be ∼0.21 nm/cycle at 70 °C, which decreased with increasing deposition temperature. Interestingly, when the deposition temperature was between 125 and 180 °C, the GPC remained almost constant at ∼0.10 nm/cycle, which suggests an ALD temperature window, whereas upon further increasing the temperature to 200 °C, the GPC considerably decreased to ∼0.04 nm/cycle. Thermodynamic analysis via density functional theory calculations showed that the self-saturation of TDMASn would occur on an NH<SUB>2</SUB>-terminated surface. Moreover, it also suggests that the condensation of a molecular precursor and the desorption of surface *NH<SUB>2</SUB> moieties would occur at lower and higher temperatures outside the ALD window, respectively. Thanks to the characteristics of ALD, this process could be used to conformally and uniformly deposit SnN<SUB><I>x</I></SUB> onto an ultranarrow dual-trench Si structure (minimum width: 15 nm; aspect ratio: ∼6.3) with ∼100% step coverage. Several analysis tools such as transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and secondary-ion mass spectrometry were used to characterize the film properties under different deposition conditions. XRD showed that a hexagonal SnN phase was obtained at a relatively low deposition temperature (100-150 °C), whereas cubic Sn<SUB>3</SUB>N<SUB>4</SUB> was formed at a higher deposition temperature (175-200 °C). The stoichiometry of these thermally grown ALD-SnN<SUB><I>x</I></SUB> films (Sn-to-N ratio) deposited at 150 °C was determined to be ∼1:0.93 with negligible impurities. The optoelectronic properties of the SnN<SUB><I>x</I></SUB> films, such as the band gap, wavelength-dependent refractive index, extinction coefficient, carrier concentration, and mobility, were further evaluated via spectroscopic ellipsometry analysis. Finally, ALD-SnN<SUB><I>x</I></SUB>-coated Ni-foam (NF) and hollow carbon nanofibers were successfully used as free-standing electrodes in electrochemical supercapacitors and in Li-ion batteries, which showed a higher charge-storage time (about eight times greater than that of the uncoated NF) and a specific capacity of ∼520 mAh/g after 100 cycles at 0.1 A/g, respectively. This enhanced performance might be due to the uniform coverage of these substrates by ALD-SnN<SUB><I>x</I></SUB>, which ensures good electric contact and mechanical stability during electrochemical reactions.</P> [FIG OMISSION]</BR>

Properties of Low-Temperature Passivation of Silicon with ALD Al_2O_3 Films and their PV Applications

Kwang-Ho Kim,Hyun-Jun Kim,Pyungwoo Jang,Chisup Jung,Kyu Seomoon,서문규 대한금속·재료학회 2011 ELECTRONIC MATERIALS LETTERS Vol.7 No.2

Low-temperature-deposited aluminium oxide (Al_2O_3) thin films were grown on p-type Si substrates by the remote plasma atomic layer deposition (RPALD) technique. The RPALD technique uses an alternative trimethylaluminum precursor and oxygen radicals to obtain good interface properties for metal-insulatorsemiconductor (MIS) inversion-layer solar cell applications. Si MIS capacitors with ultra-thin Al_2O_3 (film thickness ranges from 1 nm to 6 nm) gate dielectric and SiNx films were fabricated at 300°C and at room temperature (RT), respectively. Low-temperature-deposited Al_2O_3 and SiNx films were characterized by electrical properties such as capacitance-voltage (C-V), and current-voltage (I-V). The interface state density (Dit) of the MIS capacitors with SiNx films and without SiNx films was derived from the 1 MHz frequency C-V curves. By using ultra-thin RPALD Al_2O_3, RT-sputtered SiNx films and a simple fabrication-processing sequence, MIS solar cells were fabricated on 1 Ω·cm to 10 Ω·cm p-Si wafers. The fabricated MIS solar cell with passivated Al_2O_3 and SiNx films has 8.21% efficiency.

Low leakage current, enhanced energy storage, and fatigue endurance in room-temperature deposited (Pb0.93La0.07)(Zr0.82Ti0.18)O3 thick films

Kumar Ajeet,Lee Geon,Thakre Atul,Patil Deepak Rajaram,Han Guifang,Ryu Jungho 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.6

This study reports the fabrication of manganese (Mn) doped antiferroelectric (AFE) thick fi lms (thickness of ~ 2 μm) of (Pb0.93 La0.07 )(Zr0.82 Ti0.18 )O3 (PLZT 7/82/18) at room temperature using aerosol deposition (AD) technique without any additional thermal treatment. The Mn-doped PLZT 7/82/18 AD thick fi lms demonstrate excellent energy storage and electrical properties despite being fabricated at room temperature. The dielectric properties of the PLZT AD thick fi lms were investigated across a frequency range of 100 Hz–1 MHz and a temperature range of 25–250 o C. The Mn-doped PLZT AD thick fi lms exhibit a dielectric constant of ~ 108, low dielectric loss of 0.0211, and high-temperature stability of ~ 5.5% (from 1 kHz to 1 MHz). The bipolar P-E and I-E hysteresis loops of the PLZT AD thick fi lms do not show an AFE behavior, however, resemble the paraelectric/dielectric type of loops. The Mn-doped PLZT AD thick fi lms exhibit high dielectric breakdown strength (DBS) of ~ 5420 kV/cm, energy-storage density (ESD) of ~ 38.7 W/cm 3 , with high energy effi ciency of ~ 71%. Additionally, the Mn-doped PLZT AD thick fi lms demonstrate a low leakage current and excellent fatigue properties, as indicated by the obtained polarization, DBS, ESD, and energy effi ciency after 10 8 cycles.

Low-Temperature Growth of Indium Oxide Thin Film by Plasma-Enhanced Atomic Layer Deposition Using Liquid Dimethyl(<i>N</i>-ethoxy-2,2-dimethylpropanamido)indium for High-Mobility Thin Film Transistor Application

Kim, Hyo Yeon,Jung, Eun Ae,Mun, Geumbi,Agbenyeke, Raphael E.,Park, Bo Keun,Park, Jin-Seong,Son, Seung Uk,Jeon, Dong Ju,Park, Sang-Hee Ko,Chung, Taek-Mo,Han, Jeong Hwan American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.40

<P>Low-temperature growth of In2O3 films was demonstrated at 70-250 degrees C by plasma-enhanced atomic layer deposition (PEALD) using a newly synthesized liquid indium precursor, dimethyl(N-ethoxy-2,2-dimethylcarboxylicpropanamide)indium (Me2In(EDPA)), and O-2 plasma for application to high-mobility thin film transistors. Self-limiting In2O3 PEALD growth was observed with a saturated growth rate of approximately 0.053 nm/cycle in an ALD temperature window of 90-180 degrees C. As-deposited In2O3 films showed negligible residual impurity, film densities as high as 6.64-7.16 g/cm(3), smooth surface morphology with a root-mean-square (RMS) roughness of approximately 0.2 nm, and semiconducting level carrier concentrations of 10(17)-10(18) cm(-3). Ultrathin In2O3 channel-based thin film transistors (TFTs) were fabricated in a coplanar bottom gate structure, and their electrical performances were evaluated. Because of the excellent quality of In2O3 films, superior electronic switching performances were achieved with high field effect mobilities of 28-30 and 16-19 cm(2)/V.s in the linear and saturation regimes, respectively. Furthermore, the fabricated TFTs showed, excellent gate control characteristics in terms of subthreshold swing, hysteresis, and on/off current ratio. The low-temperature PEALD process for high-quality In2O3 films using the developed novel In precursor can be widely used in a variety of applications such as microelectronics, displays, energy devices, and sensors, especially at temperatures compatible with organic substrates.</P>

Na₂S 하부층을 이용한 Cu(In,Ga)Se₂ 광흡수층의 저온증착 및 Cu(In,Ga)Se₂ 박막태양전지에의 응용

신해나라,신영민,김지혜,윤재호,박병국,안병태,Shin, Hae Na Ra,Shin, Young Min,Kim, Ji Hye,Yun, Jae Ho,Park, Byung Kook,Ahn, Byung Tae 한국태양광발전학회 2014 Current Photovoltaic Research Vol.2 No.1

High-efficiency in $Cu(In,Ga)Se_2$ (CIGS) solar cells were usually achieved on soda-lime glass substrates due to Na incorporation that reduces deep-level defects. However, this supply of sodium from sodalime glass to CIGS through Mo back electrode could be limited at low deposition temperature. Na content could be more precisely controlled by supplying Na from known amount of an outside source. For the purpose, an $Na_2S$ layer was deposited on Mo electrode prior to CIGS film deposition and supplied to CIGS during CIGS film. With the $Na_2S$ underlayer a more uniform component distribution was possible at $350^{\circ}C$ and efficiency was improved compared to the cell without $Na_2S$ layer. With more precise control of bulk and surface component profile, CIGS film can be deposited at low temperature and could be useful for flexible CIGS solar cells.

Low-temperature Atomic Layer Deposition of TiO₂, Al₂O₃, and ZnO Thin Films

Taewook Nam,김재민,김민규,Woo-Hee Kim,김형준 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.21

We studied low-temperature atomic layer deposition (LT-ALD) of TiO₂, Al₂O₃, and ZnO thin films at temperatures down to room temperature, mainly focusing on the growth characteristics and the film’s properties. Here, two kinds of ALD deposition systems were introduced. Initially,for the thermal ALD (T-ALD) process using a commercial ALD system, a very long purging time of up to 300 s was required to entirely evacuate the remaining H₂O vapors at room temperature due to the large volume and the complicated inner structure of the commercial ALD chamber. For the realization of LT-ALD with a short process time, a plasma-enhanced ALD (PE-ALD) process using O2 plasma was employed, which enabled us to effectively remove the residual reactants at temperatures down to room temperature. As another method, we specifically designed a homemade ALD system with a small volume and a simple inner structure, thereby being able to use T-ALD to synthesize TiO₂, Al₂O₃, and ZnO thin films by using H₂O with very short H₂O purging times even at room temperature, which reveals that the chamber size and design are the critical factors enabling LT-ALD with a short process time. The LT-ALD processes produced highly-pure Al₂O₃,TiO₂, and ZnO films without any C and N impurities by complete elimination of ligands and exhibited excellent conformality in 3-dimensional nanoscale via holes.

화학 기상 증착법을 통한 저온 그래핀 합성 연구 개발 동향

최준희,이재현 한국세라믹학회 2022 세라미스트 Vol.25 No.4

Graphene, a one-atom-thick crystal of carbon, has attracted tremendous attention for various electrical and energy applications due to its superior physical and chemical properties. Among various graphene synthetic approaches, the CVD method has been considered a promising way to obtain high-quality graphene in large-scale. H owever, to obtain high-quality graphene by a typical CVD process, a high temperature of 1000 ℃ or higher should be required to decompose the hydrocarbon precursors, which is a major obstacle to the commercialization of CVD-graphene. Recently, enormous research has been conducted to grow high-quality graphene at a low temperature using various hydrocarbon precursors and external energy sources. H ere, we briefly review recent research progress in the low-temperature growth of graphene using CVD methods. In addition, we introduce representative electronic applications based on low-temperature CVD-graphene.