Abstract:Phase change memory (PCM) is a rapidly growing technology that not only offers advancements in storage-class memories but also enables in-memory data processing to overcome the von Neumann bottleneck. In PCMs, data storage is driven by thermal excitation. However, there is limited research regarding PCM thermal properties at length scales close to the memory cell dimensions. Our work presents a new paradigm to manage thermal transport in memory cells by manipulating the interfacial thermal resistance between t… Show more
“…1 d), which could suggest incomplete crystallization or minor damage from sample preparation; similar observations are found in the 20 nm crystalline GSST film. A ~5% thickness reduction is measured upon crystallization in both 20 and 150 nm films indicating densification of GSST after the phase transformation, similar to previous observations in GST 17 , 35 . Fig.…”
Section: Resultssupporting
confidence: 88%
“…In chalcogenide-based PCMs, thermal excitation can induce reversible solid-state phase transitions between amorphous and crystalline states 13 , 14 . This phase transition is non-volatile and leads to large contrasts in the electrical 15 , optical 16 , and thermal properties 17 . Germanium antimony telluride, Ge−Sb−Te (GST), is the most popular and the most studied chalcogenide-based PCMs due to its phase stability 14 , large property contrast 18 , and fast switching rate 19 , 20 .…”
Integrated nanophotonics is an emerging research direction that has attracted great interests for technologies ranging from classical to quantum computing. One of the key-components in the development of nanophotonic circuits is the phase-change unit that undergoes a solid-state phase transformation upon thermal excitation. The quaternary alloy, Ge2Sb2Se4Te, is one of the most promising material candidates for application in photonic circuits due to its broadband transparency and large optical contrast in the infrared spectrum. Here, we investigate the thermal properties of Ge2Sb2Se4Te and show that upon substituting tellurium with selenium, the thermal transport transitions from an electron dominated to a phonon dominated regime. By implementing an ultrafast mid-infrared pump-probe spectroscopy technique that allows for direct monitoring of electronic and vibrational energy carrier lifetimes in these materials, we find that this reduction in thermal conductivity is a result of a drastic change in electronic lifetimes of Ge2Sb2Se4Te, leading to a transition from an electron-dominated to a phonon-dominated thermal transport mechanism upon selenium substitution. In addition to thermal conductivity measurements, we provide an extensive study on the thermophysical properties of Ge2Sb2Se4Te thin films such as thermal boundary conductance, specific heat, and sound speed from room temperature to 400 °C across varying thicknesses.
“…1 d), which could suggest incomplete crystallization or minor damage from sample preparation; similar observations are found in the 20 nm crystalline GSST film. A ~5% thickness reduction is measured upon crystallization in both 20 and 150 nm films indicating densification of GSST after the phase transformation, similar to previous observations in GST 17 , 35 . Fig.…”
Section: Resultssupporting
confidence: 88%
“…In chalcogenide-based PCMs, thermal excitation can induce reversible solid-state phase transitions between amorphous and crystalline states 13 , 14 . This phase transition is non-volatile and leads to large contrasts in the electrical 15 , optical 16 , and thermal properties 17 . Germanium antimony telluride, Ge−Sb−Te (GST), is the most popular and the most studied chalcogenide-based PCMs due to its phase stability 14 , large property contrast 18 , and fast switching rate 19 , 20 .…”
Integrated nanophotonics is an emerging research direction that has attracted great interests for technologies ranging from classical to quantum computing. One of the key-components in the development of nanophotonic circuits is the phase-change unit that undergoes a solid-state phase transformation upon thermal excitation. The quaternary alloy, Ge2Sb2Se4Te, is one of the most promising material candidates for application in photonic circuits due to its broadband transparency and large optical contrast in the infrared spectrum. Here, we investigate the thermal properties of Ge2Sb2Se4Te and show that upon substituting tellurium with selenium, the thermal transport transitions from an electron dominated to a phonon dominated regime. By implementing an ultrafast mid-infrared pump-probe spectroscopy technique that allows for direct monitoring of electronic and vibrational energy carrier lifetimes in these materials, we find that this reduction in thermal conductivity is a result of a drastic change in electronic lifetimes of Ge2Sb2Se4Te, leading to a transition from an electron-dominated to a phonon-dominated thermal transport mechanism upon selenium substitution. In addition to thermal conductivity measurements, we provide an extensive study on the thermophysical properties of Ge2Sb2Se4Te thin films such as thermal boundary conductance, specific heat, and sound speed from room temperature to 400 °C across varying thicknesses.
“…In the amorphization process of RESET, a large current is applied to heat the phase change layer above the melting temperature while smaller current is required for the crystallization SET. In this regard, innovative methods for structural and material engineering have been demonstrated to reduce the amorphization current [97][98][99][100][101]. You et al suggested a hybrid PCM architecture of TiW/Ge2Sb2Te5 (GST)/ NiO/Ni to control the crystallinity of GST with self-structured Ni filaments [102].…”
Section: Recent Advances In Nonvolatile Memoriesmentioning
The unstructured data such as visual information, natural language, and human behaviors opens up a wide array of opportunities in the field of artificial intelligence (AI). The memory-centric neuromorphic computing (MNC) has been proposed for the efficient processing of unstructured data, bypassing the von Neumann bottleneck of current computing architecture. The development of MNC would provide massively parallel processing of unstructured data, realizing the cognitive AI in edge and wearable systems. In this review, recent advances in memory-centric neuromorphic devices are discussed in terms of emerging nonvolatile memories, volatile switches, synaptic plasticity, neuronal models, and memristive neural network.
“…As one of the most promising candidates for next-generation nonvolatile new memories, phase change memory (PCM) has garnered much attention due to its high-speed cell operation, good reliability, and excellent scalability. [1][2][3][4][5][6][7][8] A PCM cell, which exploits the phase transition characteristic of chalcogenide materials, shows a difference in the resistance of roughly two orders between a low resistance state (LRS, crystalline) and a high resistance state (HRS, amorphous). [4] In order to change the LRS to a HRS, high…”
writing current is required due to the high melting point (≈888 K @ Ge 2 Sb 2 Te 5 , GST) of the phase-switching active material. [9] In general, the writing current is highly dependent on the pattern size, contact area between active layer and heater, and material composition of active thin film, bottom electrode contact, and top electrode (TE). [10] In particular, the switching or writing current of a PCM cell scales with the phasechanging volume from the crystalline to the amorphous state in a phase-change material. [2,11] However, the scaling down of PCM arrays to reduce the power consumption for PCM cell operation is becoming more difficult due to the physical diffraction limitation of photolithography. [12] Hence, to achieve low power operation of a PCM device, many memory-research groups have studied the development of new phase-change materials and have attempted to design innovative device structures. [13][14][15] Nanopatterning refers to a process to fabricate periodic nanoscale structures with sub-100 nm feature sizes applicable to various electronic devices with complex nanoscale circuit designs. [16][17][18][19][20][21] Over the last several decades, as an advanced nanopatterning method, the self-assembly of block copolymers (BCPs) has attracted much attention due to its ultrafine pattern resolution, excellent scalability, morphological tunability, and reliable compatibility with conventional semiconducting processes. [22][23][24][25][26][27][28][29][30] BCPs can self-assemble into the various nanoscale morphologies though the microphase separation process and/or minimization of Gibbs free energy. [31][32][33] In particular, di-BCP with a high Flory-Huggins interaction parameter (χ) consisting of two immiscible polymer blocks can produce well-ordered pattern geometries with a range of 10-50 nm through the nanoscale phase-separation phenomenon. [34][35][36] Many BCP research groups have reported various advanced BCP nanopatterning methods that can be used to manipulate the pattern geometry, morphological tunability, pattern scalability, and functionality of BCPs with a high χ value. [31,[37][38][39][40] We have also demonstrated how effectively to obtain a variety of functional BCP nanostructures over a large area, such as dot, line, hole, and dot-in-hole patterns. [32,41,42] Other, BCP groups have demonstrated several electronic device applications of self-assembled functional BCPs, such as resistive memory, magnetic storage device, and PCM. [43][44][45][46][47] Although innovative BCP-based PCM studies focusing on low power consumption exist, more practical and effective strategies are still needed to realize the smart The phase change memory (PCM) is one of the key enabling memory technologies for next-generation non-volatile memory device applications due to its high writing speed, excellent endurance, long retention time, and good scalability. However, the high power consumption of PCM devices caused by the high switching current from a high resistive state to a low resistive state is a critical ...
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