This paper aims to build up a preference function to evaluate the public benefits of the type of agricultural farming, biodiversity, water provisions, land use type, ecotourism modes, and a monetary attribute (willingness to pay and willingness to work) associated with an ecosystem service and land use program in a forest park. This study used choice experiments to build a random utility model, analyze the average preference for the above land use attributes based on the conditional logit (CL) and used a latent class model to test the residents' heterogeneous preferences for land use planning in the forest park. We also estimated the welfare derived from various land use programs. The empirical result has shown that: (1) increasing organic farming area, increasing the surface water provision, increasing the area of custom flora, increasing the wetland area, and setting up an integrated framework for ecotourism increase the public's preference for the land use program; (2) farmer and non-farmers do not have the same land use preferences, attributes, marginal willingness to pay and willingness to work; and (3) the ecotourism development program incorporating biodiversity, organic farming, ethnobotany, and wetland area with integrated ecotourism has the highest values when compared to other land use program scenarios.
Phase transition kinetics and microstructures of AgInSbTe ͑AIST͒ and AIST-SiO 2 nanocomposite applied to phase-change memories ͑PCMs͒ are investigated. In situ electrical property measurement found that the incorporation of SiO 2 escalates the recrystallization temperature ͑T x ͒ of nanocomposite. Both X-ray diffraction and transmission electron microscopy showed grain refinement in the nanocomposite which, in turn, results in an increase of the activation energy ͑E a ͒ of phase transition, as indicated by subsequent Kissinger's analysis. Increase of T x and E a in the nanocomposite was ascribed to AIST grain refinement and hindrance to grain growth due to dispersed SiO 2 particles in the sample matrix. Johnson-Mehl-Avrami analysis revealed the decrease of Avrami exponent in nanocomposite, implying that the dispersed SiO 2 particles promote the heterogeneous phase transition. Static I-V characteristics and reversible binary switching behavior of PCM devices not only confirmed the results of microstructure characterizations but also illustrated the feasibility of the AIST and its nanocomposite layer for PCM fabrication.Phase-change memory ͑PCM͒ has been recognized as nextgeneration nonvolatile memory device due to its advantages, including good scalability, high operation speed, low power consumption, high recording density, signal endurance, etc. 1-9 Instead of using laser beam as the heating source in optical data storage, PCM devices utilize a current pulse to heat the phase-change programming layer embedded in devices for signal recording. In order to reduce operating current of PCM devices, various methods have been proposed. One is to define a smaller programming volume by modifying the PCM cell structure, while the other is to modify the physical properties of phase-change materials by, for instance, increasing the resistivity of the phase-change layer in the crystalline state by doping a small amount of nitrogen ͑N͒, 1,2 oxygen ͑O͒, 3,4 silicon ͑Si͒, 5,6 silicon oxide ͑SiO x ͒, 7-9 etc.In contrast to the nucleation-dominated GeSbTe ͑GST͒ alloys, binary Sb 2 Te alloys are termed as the growth-dominated chalcogenides. 10 In practice, Sb 2 Te alloys are usually doped with desired elements for physical property improvement. 11 The Sb 2 Te alloys doped with silver ͑Ag͒ and indium ͑In͒, i.e., the quaternary AgInSbTe ͑AIST͒, are known to possess better cycling stability of amorphous phase and higher crystallization sensitivity in comparison with other phase-change materials. 12,13 Further, the study on digital versatile disk containing AIST illustrated that the disk possesses high recording density and data-transfer rate features. 14 Good optical properties imply that AIST might also be a promising material for PCM application. However, the electrical properties of AIST are less reported and a further study to identify its feasibility to PCM is required.Previous studies reported that incorporating SiO 2 in GST may effectively improve the stability of amorphous GST and reduce the reset current of PCM devices. 8,9 ...
A study on microstructure and electrical property of cerium (Ce)-doped Ge2Sb2Te5 (GST) layers for phase-change memory (PCM) application were presented. Ce doping does not suppress the resistivity of amorphous GST and the resistivity ratio of amorphous and crystalline GST remains at about 105. Further, Ce-doping escalates the recrystallization temperature (Tx) of GST from 159 to 236°C. Such a unique behavior would greatly benefit the preservation of signal contrast as well as the high-density signal storage and will not cause the increase of device writing current. X-ray diffraction (XRD) indicated that Ce doping stabilizes amorphous GST and suppresses the formation of hexagonal phase. Transmission electron microscopy (TEM) revealed Ce doping refines the grain size of GST. Kissinger's analysis found that Tx and activation energy (Ea) of phase transition for doped-GST both increase with the increase of Ce content. Isothermal experiment found the Ce doping increases temperature for 10-yr data retention from 76 and 170°C. This is attributed to the presence of Ce solutes in GST matrix that inhibits the grain growth during recrystallization.Static-mode electrical test on PCM device containing doped GST as the programming layer found that Ce incorporation indeed increases the switching threshold voltage (Vth). This confirmed that Ce doping effectively retards the crystallization of GST and improves the stability of amorphous GST.
Phase-change kinetics, structure evolution and feasibility to phase-change memory (PCM) of Ag2In7Sb64Te27 (AIST) and its nanocomposite comprised of 85 wt.% AIST and 15 wt.% SiO2 were presented. In-situ heating x-ray diffraction (XRD) indicated nanocomposite transforms from amorphous to HCP structure during heating and incorporation of SiO2 increases the recrystallization temperature (Tx) of samples (189°C for AIST and 223°C for nanocomposite). XRD and transmission electron microscopy (TEM) analyses both revealed the grain refinement in nanocomposite. Kissinger's analysis found the increase of activation energy (Ea) of phase transition in nanocomposite, denoting the SiO2 embedment restrains the grain growth of AIST during recrystallization. Johnson-Mehl-Avrami (JMA) theory revealed the decrease of Avrami exponent (n), indicating that the phase transition is prone to be heterogeneous since the dispersed SiO2 particles may provide additional nucleation sites.Static I–V measurement indicated that the switching threshold voltage (Vth) of nanocomposite device (1.65 V) is higher than that of the AIST device (1.10 V). Increase of dynamic resistance in nanocomposite device leads to the reduction of writing current. I–V analysis also confirmed the retardation of recrystallization in AIST due to the incorporation of SiO2 and the rise of Ea is able to enhance the thermal stability of amorphous state in PCM devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.