Browsing by Author "Chang, Chia-Fu"

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Direct Observation of Dual-Filament Switching Behaviors in Ta2O5-Based Memristors
(2017-04-18)
Chang, Chia-Fu
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Chen, Jui-Yuan
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Huang, Chun-Wei
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Chiu, Chung-Hua
;
Lin, Ting-Yi
In Situ Investigation of Defect-Free Copper Nanowire Growth
(2018-02-01)
Lin, Ting-Yi
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Chen, Yong-Long
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Chang, Chia-Fu
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Huang, Guan-Min
;
Huang, Chun-Wei
The fabrication and placement of high purity nanometals, such as one-dimensional copper (Cu) nanowires, for interconnection in integrated devices have been among the most important technological developments in recent years. Structural stability and oxidation prevention have been the key issues, and the defect control in Cu nanowire growth has been found to be important. Here, we report the synthesis of defect-free single-crystalline Cu nanowires by controlling the surface-assisted heterogeneous nucleation of Cu atomic layering on the graphite-like loop of an amorphous carbon (a-C) lacey film surface. Without a metal-catalyst or induced defects, the high quality Cu nanowires formed with high aspect ratio and high growth rate of 578 nm/s. The dynamic study of the growth of heterogeneous nanowires was conducted in situ with a high-resolution transmission electron microscope. The study illuminates the new mechanism by heterogeneous nucleation control and laying the groundwork for better understanding of heterosurface-assisted nucleation of defect-free Cu nanowire on a-C lacey film.
In-situ TEM observation of Multilevel Storage Behavior in low power FeRAM device
(2017-04-01)
Chiu, Chung-Hua
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Huang, Chun-Wei
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Hsieh, Ying-Hui
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Chen, Jui-Yuan
;
Chang, Chia-Fu
The quest for non-volatile memories has attracted tremendous attention, especially in mature ferroelectric random access memory (FeRAM) with properties of high read/write speed and low power consumption. Strain engineering of multiferroic BiFeO3 (BFO) has recently become the subject of broad research interest because of its intriguing properties. In this study, we demonstrate the switchable diode characteristics in highly strained BFO thin films. Using a unique in situ electrical transmission electron microscopy (TEM), we verify the correlation between ferroelectric resistive switching with multilevel states and polarization reversal. Structural investigation confirms that the phase transition from mixed phase to pure T-like phase, accompanying with the polarization reversal by external bias, is the origin of the multilevel states. The switchable diode with multilevel resistive switching can be explained in terms of the variation of the barrier height, governed by ferroelectric polarization and polarity of the external bias. This research model, i.e., engineering of the room inside, can offer an approach toward high-density memories.
Nickel/Platinum Dual Silicide Axial Nanowire Heterostructures with Excellent Photosensor Applications
(2016-02)
Wu, Yen-Ting
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Huang, Chun-Wei
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Chiu, Chung-Hua
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Chang, Chia-Fu
;
Chen, Jui-Yuan
Transition metal silicide nanowires (NWs) have attracted increasing attention as they possess advantages of both silicon NWs and transition metals. Over the past years, there have been reported with efforts on one silicide in a single silicon NW. However, the research on multicomponent silicides in a single silicon NW is still rare, leading to limited functionalities. In this work, we successfully fabricated beta-Pt2Si/Si/theta-Ni2Si, beta-Pt2Si/theta-Ni2Si, and Pt, Ni, and Si ternary phase axial NW heterostructures through solid state reactions at 650 degrees C. Using in situ transmission electron microscope (in situ TEM), the growth mechanism of silicide NW heterostructures and the diffusion behaviors of transition metals were systematically studied. Spherical aberration corrected scanning transmission electron microscope (Cs-corrected STEM) equipped with energy dispersive spectroscopy (EDS) was used to analyze the phase structure and composition of silicide NW heterostructures. Moreover, electrical and photon properties for the silicide nanowire heterostructures demonstrated promising applications in nano-optoeletronic devices. We found that Ni, Pt, and Si ternary phase nanowire heterostructures have an excellent infrared light sensing property which is absent in bulk Ni2Si or Pt2Si. The above results would benefit the further understanding of heterostructured nano materials. sensing
Revealing conducting filament evolution in low power and high reliability Fe3O4/Ta2O5 bilayer RRAM
(2018-11-01)
Chang, Chia-Fu
;
Chen, Jui-Yuan
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Huang, Guan-Min
;
Lin, Ting-Yi
;
Tai, Kuo-Lun
In this work, we used the polycrystalline-Fe3O4 to improve the reliability of the Ag/Ta2O5/Pt resistive random access memory (RRAM). In both the Ag/Ta2O5/Fe3O4/Pt and Ag/Fe3O4/Ta2O5/Pt structures, the switching properties for these bilayer RRAMs were measured in atmosphere and vacuum environments. The results demonstrated that the humidity would affect the Ag filament formation in different environments, and the Ta2O5 and Fe3O4 interface in a different sequence would change the performance of the device, particularly the Forming voltage. Furthermore, the switching voltage and reliability of these bilayer RRAMs was better than single-layer RRAM device, which significantly increased endurance, especially in the Ag/Fe3O4/Ta2O5/Pt device. We also observed the conducting filament shape and evolution during Forming via in/ex-situ transmission electron microscopy (TEM) in the Ag/Fe3O4/Ta2O5/Pt system. In low humidity, the conducting filament was composed of many weak filaments in a low-resistance state (LRS), where the grain boundaries in the Fe3O4 layer limited filament size. The results of energy dispersive spectrometry (EDS) analysis demonstrated that the filament was composed of Ag metal. This study provided detailed switching knowledge of the bilayer RRAM for improving the reliability and power consumption of the device and new design viewpoints of the RRAM structure in future applications.
Synthesis of single-crystalline Ge1Sb2Te4 nanoplates in solution phase
(2016)
Huang, Wei-Hsiang
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Gao, Tzu-Lun
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Huang, Chun-Wei
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Chang, Chia-Fu
;
Wu, Wen-Wei
A chemical route to synthesize single-crystalline Ge1Sb2Te4 (GST-124) hexagonal nanoplatelets is reported, showing the first example of obtaining colloidal GeSbTe nanoalloys in solution phase.