Kim, Jiyoung
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/2484
Jiyoung Kim serves as Associate Professor in the Department of Materials Science and Engineering. His research interests include:
- Gate Stack Engineering for the Next Generation Complementary
- Metal-Oxide-Semiconductor (CMOS) Applications
- Nano-structure Materials and Devices for Nanoelectronics
- Novel Atomic Layer Deposition (ALD) Applications
- Novel Memory Device Materials, Fabrication and Applications
- Nano-sensor Fabrication and Applications
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Browsing Kim, Jiyoung by Author "0000-0003-2781-5149 (Kim, J)"
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Item Engineering The Palladium-WSe₂ Interface Chemistry for Field Effect Transistors with High-Performance Hole Contacts(Amer Chemical Soc, 2018-12-07) Smyth, Christopher M.; Walsh, Lee A.; Bolshakov, Pavel; Catalano, Massimo; Addou, Rafik; Wang, Luhua; Kim, Jiyoung; Kim, Moon J.; Young, Chadwin D.; Hinkle, Christopher L.; Wallace, Robert M.; 0000-0001-5566-4806 (Wallace, RM); 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 0000-0002-6688-8626 (Walsh, LA); 0000-0002-5485-6600 (Hinkle, CD); 0000-0002-5454-0315 (Addou, R); 70133685 (Kim, J); Smyth, Christopher M.; Walsh, Lee A.; Bolshakov, Pavel; Catalano, Massimo; Addou, Rafik; Wang, Luhua; Kim, Jiyoung; Kim, Moon J.; Young, Chadwin D.; Hinkle, Christopher L.; Wallace, Robert M.Palladium has been widely employed as a hole contact to WSe₂ and has enabled, at times, the highest WSe₂ transistor performance. However, there are orders of magnitude variation across the literature in Pd-WSe₂ contact resistance and I-ON/I-OFF ratios with no true understanding of how to consistently achieve high-performance contacts. In this work, WSe₂ transistors with impressive I-ON/I-OFF ratios of 10(6) and Pd-WSe₂ Schottky diodes with near-zero variability are demonstrated utilizing Ohmic-like Pd contacts through deliberate control of the interface chemistry. The increased concentration of a PdSeₓ intermetallic is correlated with an Ohmic band alignment and concomitant defect passivation, which further reduces the contact resistance, variability, and barrier height inhomogeneity. The lowest contact resistance occurs when a 60 min post-metallization anneal at 400 degrees C in forming gas (FG) is performed. X-ray photoelectron spectroscopy indicates this FG anneal produces 3x the concentration of PdSeₓ and an Ohmic band alignment, in contrast to that detected after annealing in ultrahigh vacuum, during which a 0.2 eV hole Schottky barrier forms. Raman spectroscopy and scanning transmission electron microscopy highlight the necessity of the fabrication step to achieve high-performance contacts as no PdSeₓ forms, and WSe₂ is unperturbed by room temperature Pd deposition. However, at least one WSe₂ layer is consumed by the necessary interface reactions that form PdSeₓ requiring strategic exploitation of a sacrificial WSe₂ layer during device fabrication. The interface chemistry and structural properties are correlated with Pd-WSe₂ diode and transistor performance, and the recommended processing steps are provided to enable reliable high-performance contact formation.Item Ferroelectric Hf₀․₅Zr₀․₅O₂ Thin Films: A Review of Recent Advances(Springer, 2018-09-28) Kim, Si Joon; Mohan, Jaidah; Summerfelt, Scott R.; Kim, Jiyoung; 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Mohan, Jaidah; Kim, JiyoungFerroelectricity in HfO₂-based materials, especially Hf₀․₅Zr₀․₅O₂ (HZO), is today one of the most attractive topics because of its wide range of applications in ferroelectric random-access memory, ferroelectric field-effect transistors, ferroelectric tunneling junctions, steep-slope devices, and synaptic devices. The main reason for this increasing interest is that, when compared with conventional ferroelectric materials, HZO is compatible with complementary metal-oxide-semiconductor flow [even back-end of the line thermal budget] and can exhibit robust ferroelectricity even at extremely thin (<10nm) thicknesses. In this report, recent advances in the ferroelectric properties of HZO thin films since the first report in 2011, including doping effects, mechanical stress effects, interface effects, and ferroelectric film thickness effects, are comprehensively reviewed.Item Ferroelectric TiN/Hf₀.₅Zr₀.₅O₂/Tin Capacitors with Low-Voltage Operation and High Reliability for Next-Generation FRAM Applications(Institute of Electrical and Electronics Engineers Inc.) Kim, Si Joon; Mohan, Jaidah; Young, Chadwin D.; Colombo, Luigi; Kim, Jiyoung; Summerfelt, S. R.; San, T.; 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Si Joon; Mohan, Jaidah; Young, Chadwin D.; Colombo, Luigi; Kim, JiyoungIn this study, we investigated the ferroelectric properties of Hf₀.₅Zr₀.₅O₂ (HZO) thin films with different thicknesses (5-20 nm) deposited by atomic layer deposition for the development of future ferroelectric random access memory cells. HZO-based capacitors with a thickness of 5 nm exhibited a switching polarization of ~13 μC/cm² and a ferroelectric saturation voltage of 1.0 V as extracted from the pulse write/read measurements. Furthermore, we performed fatigue measurements and we found no degradation up to 10¹⁰ switching cycles at 1.2 V.Item High-κ Dielectric on ReS₂: In-Situ Thermal Versus Plasma-Enhanced Atomic Layer Deposition of Al₂O₃(MDPI AG, 2019-03-30) Khosravi, Ava; Addou, Rafik; Catalano, Massimo; Kim, Jiyoung; Wallace, Robert M.; 0000-0003-2781-5149 (Kim, J); 0000-0001-5566-4806 (Wallace, RM); 0000-0001-9901-9809 (Khosravi, A); 0000-0002-5454-0315 (Addou, R); 70133685 (Kim, J); Khosravi, Ava; Addou, Rafik; Catalano, Massimo; Kim, Jiyoung; Wallace, Robert M.We report an excellent growth behavior of a high-κ dielectric on ReS₂ , a two-dimensional (2D) transition metal dichalcogenide (TMD). The atomic layer deposition (ALD) of an Al₂O₃ thin film on the UV-Ozone pretreated surface of ReS₂ yields a pinhole free and conformal growth. In-situ half-cycle X-ray photoelectron spectroscopy (XPS) was used to monitor the interfacial chemistry and ex-situ atomic force microscopy (AFM) was used to evaluate the surface morphology. A significant enhancement in the uniformity of the Al₂O₃ thin film was deposited via plasma-enhanced atomic layer deposition (PEALD), while pinhole free Al₂O₃ was achieved using a UV-Ozone pretreatment. The ReS₂ substrate stays intact during all different experiments and processes without any formation of the Re oxide. This work demonstrates that a combination of the ALD process and the formation of weak S-O bonds presents an effective route for a uniform and conformal high-κ dielectric for advanced devices based on 2D materials. © 2019 by the authors.Item Large Ferroelectric Polarization of TiN/Hf₀․₅Zr₀․₅0₂ Capacitors Due to Stress-Induced Crystallization at Low Thermal Budget(Amer Inst Physics, 2018-10-22) Kim, Si Joon; Narayan, Dushyant; Lee, Jae-Gil; Mohan, Jaidah; Lee, Joy S.; Lee, Jaebeom; Kim, Harrison S.; Byun, Young-Chul; Lucero, Antonio T.; Young, Chadwin D.; Summerfelt, Scott R.; San, Tamer; Colombo, Luigi; Kim, Jiyoung; 0000-0001-7335-1053 (Lee, JS); 0000-0001-9477-5728 (Byun, Y-C); 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Si Joon; Narayan, Dushyant; Lee, Jae-Gil; Mohan, Jaidah; Lee, Joy S.; Lee, Jaebeom; Kim, Harrison S.; Byun, Young-Chul; Lucero, Antonio T.; Young, Chadwin D.; Kim, JiyoungWe report on atomic layer deposited Hf₀․₅Zr₀․₅0₂ (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm²) and a low FE saturation voltage (~1.5V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centrosymmetric orthorhombic phase, which is enabled by the TiN top electrode (TE) having a thickness of at least 90nm. The TiN films are deposited at room temperature and annealed at 400 ⁰C in an inert environment for at least 1 min in a rapid thermal annealing system. The room-temperature deposited TiN TE acts as a tensile stressor on the HZO film during the annealing process. The stress-inducing TiN TE is shown to inhibit the formation of the monoclinic phase during HZO crystallization, forming an orthorhombic phase that generates a large FE polarization, even at low process temperatures.Item Organic-Inorganic Hybrid Semiconductor Thin Films Deposited Using Molecular-Atomic Layer Deposition (MALD)(Royal Society of Chemistry) Huang, Jie; Zhang, Hengji; Lucero, Antonio; Cheng, Lanxia; KC, Santosh; Wang, Jian; Hsu, Julia W. P.; Cho, Kyeongjae; Kim, Jiyoung; 0000 0003 8600 0978 (Hsu, JWP); 0000-0003-2698-7774 (Cho, K); 0000-0003-2781-5149 (Kim, J); Huang, Jie; Zhang, Hengji; Lucero, Antonio; Cheng, Lanxia; KC, Santosh; Wang, Jian; Hsu, Julia W. P.; Cho, Kyeongjae; Kim, JiyoungMolecular-atomic layer deposition (MALD) is employed to fabricate hydroquinone (HQ)/diethyl zinc (DEZ) organic-inorganic hybrid semiconductor thin films with accurate thickness control, sharp interfaces, and low deposition temperature. Self-limiting growth is observed for both HQ and DEZ precursors. The growth rate remains constant at approximately 2.8 Å per cycle at 150°C. The hybrid materials exhibit n-type semiconducting behavior with a field effect mobility of approximately 5.7 cm² V⁻¹ s⁻¹ and an on/off ratio of over 103 following post annealing at 200°C in nitrogen. The resulting films are characterized using ellipsometry, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV-Vis spectroscopy, transistor behavior, and Hall-effect measurements. Density functional theory (DFT) and many-body perturbation theory within the GW approximation are also performed to assist the explanation and understanding of the experimental results. This research offers n-channel materials as valuable candidates for efficient organic CMOS devices. © 2016.Item Realization of Spatially Addressable Library by a Novel Combinatorial Approach on Atomic Layer Deposition: A Case Study of Zinc Oxide(American Chemical Society, 2019-05-07) Kim, Harrison Sejoon; Lee, Joy S.; Kim, S. J.; Lee, Jaebeom; Lucero, Antonio T.; Sung, M. M.; Kim, Jiyoung; 0000-0003-2781-5149 (Kim, J); 0000-0002-6488-5915 (Kim, HS); 70133685 (Kim, J); Kim, Harrison Sejoon; Lee, Joy S.; Lee, Jaebeom; Lucero, Antonio T.; Kim, JiyoungThough the synthesis of libraries of multicomponent metal oxide systems is prevalent using the combinatorial approach, the combinatorial approach has been rarely realized in studying simple metal oxides, especially applied to the atomic layer deposition (ALD) technique. In this literature, a novel combinatorial approach technique is utilized within an ALD grown simple metal oxide to synthesize a "spatially addressable combinatorial library". The two key factors in gradients were defined during the ALD process: (1) the process temperature and (2) a nonuniform flow of pulsed gases inside a cross-flow reactor. To validate the feasibility of our novel combinatorial approach, a case study of zinc oxide (ZnO), a simple metal oxide whose properties are well-known, is performed. Because of the induced gradient, the ZnO (002) crystallite size was found to gradually vary across a 100 mm wafer (10-20 nm) with a corresponding increase in the normalized Raman E 2 /A 1 peak intensity ratio. The findings agree well with the visible grain size observed from scanning electron microscope. The novel combinatorial approach provides a means of systematical interpretation of the combined effect of the two gradients, especially in the analysis of the microstructure of ZnO crystals. Moreover, the combinatorial library reveals that the process temperature, rather than the crystal size, plays the most significant role in determining the electrical conductivity of ZnO. © 2019 American Chemical Society.Item Top-Down Fabrication of High-Uniformity Nanodiamonds by Self-Assembled Block Copolymer Masks(Nature Publishing Group) Bersin, E.; Cotlet, M.; Doerk, G.; Lienhard, B.; Zheng, J; Kim, Harrison Sejoon; Byun, Young-Chui; Nam, C. -Y.; Kim, Jiyoung; Black, C. T.; Englund, D.; 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Harrison Sejoon; Byun, Young-Chui; Kim, JiyoungNanodiamonds hosting colour centres are a promising material platform for various quantum technologies. The fabrication of non-aggregated and uniformly-sized nanodiamonds with systematic integration of single quantum emitters has so far been lacking. Here, we present a top-down fabrication method to produce 30.0 ± 5.4 nm uniformly-sized single-crystal nanodiamonds by block copolymer self-assembled nanomask patterning together with directional and isotropic reactive ion etching. We show detected emission from bright single nitrogen vacancy centres hosted in the fabricated nanodiamonds. The lithographically precise patterning of large areas of diamond by self-assembled masks and their release into uniformly sized nanodiamonds open up new possibilities for quantum information processing and sensing. ©2019, The Author(s).Item ZnO Composite Nanolayer with Mobility Edge Quantization for Multi-Value Logic Transistors(Nature Publishing Group, 2019-04-30) Lee, L.; Hwang, Jeongwoon; Jung, J. W.; Kim, J.; Lee, H. -I; Heo, S.; Yoon, M.; Choi, S.; Van Long, N.; Park, J.; Jeong, J. W.; Kim, Jiyoung; Kim, K. R.; Kim, D. H.; Im, S.; Lee, B. H.; Cho, Kyeongjae; Sung, M. M.; 0000-0003-2781-5149 (Kim, J); 0000-0003-2698-7774 (Cho, K); 70133685 (Kim, J); 369148996084659752200 (Cho, K); Hwang, Jeongwoon; Kim, Jiyoung; Cho, KyeongjaeA quantum confined transport based on a zinc oxide composite nanolayer that has conducting states with mobility edge quantization is proposed and was applied to develop multi-value logic transistors with stable intermediate states. A composite nanolayer with zinc oxide quantum dots embedded in amorphous zinc oxide domains generated quantized conducting states at the mobility edge, which we refer to as “mobility edge quantization”. The unique quantized conducting state effectively restricted the occupied number of carriers due to its low density of states, which enable current saturation. Multi-value logic transistors were realized by applying a hybrid superlattice consisting of zinc oxide composite nanolayers and organic barriers as channels in the transistor. The superlattice channels produced multiple states due to current saturation of the quantized conducting state in the composite nanolayers. Our multi-value transistors exhibited excellent performance characteristics, stable and reliable operation with no current fluctuation, and adjustable multi-level states. ©2019, The Author(s).