No abstract

No abstract

The technological success of phase-change materials in the field of data storage and functional systems stems from their distinctive electronic and structural peculiarities on the nanoscale. Recently, superlattice structures have been demonstrated to dramatically improve the optical and electrical performances of these chalcogenide based phase-change materials. In this perspective, unravelling the atomistic structure that originates the improvements in switching time and switching energy is paramount in order to design nanoscale structures with even enhanced functional properties. This study reveals a high-resolution atomistic insight of the [GeTe/Sb 2 Te 3 ] interfacial structure by means of Extended X-Ray Absorption Fine Structure spectroscopy and Transmission Electron Microscopy. Based on our results we propose a consistent novel structure for this kind of chalcogenide superlattices.The need for fast and efficient management of information stimulates research on materials that can be switched on nanometer length scales and sub-nanosecond time scales. Phase-Change materials (PCMs) possess a unique property portfolio, which is ideally suited for memory device applications [1][2][3][4][5][6] . A PCM is identified by its ability of switching rapidly and reversibly between a crystalline and an amorphous state, where the amorphous state is obtained by melting the crystalline state followed by rapid quenching. These two states significantly differ in their properties, such as the optical reflectivity as well as the electrical conductivity. The phase transformation is in general triggered by thermal heating, or by either electrical and optical pulses of different time duration and amplitude. The large contrast in reflectivity between these two states lays at the base of already working PCM-based optical rewritable media devices-like DVDs or Blu-Ray Disc-where information is encoded as amorphous marks in a crystalline background. The contrast in resistivity could be exploited in the next generation of electronic solid-state memories based on PCMs, which might replace the current leading storage technologies, namely FLASH and magnetic disks. Furthermore, these materials could be employed in displays or data visualization applications by combining both their optical and electronic property modulations 7 . Hence, a lot of interest and effort is currently devoted to uncover the complex physical origin of the high contrast between the two phases [8][9][10]

No abstract

Abstract-A systematic design of practicable media suitable for re-writeable, ultra-high density (> 1Tbit/sq.in.), high data rate (> 1Mbit/s/tip) scanning probe phase-change memories is presented. The basic design requirements were met by a Si/TiN/GST/DLC structure, with properly tailored electrical and thermal conductivities. Various alternatives for providing re-writeability were investigated. In the first case amorphous marks were written into a crystalline starting phase and subsequently erased by re-crystallization, as in other already-established phasechange memory technologies. Results imply that this approach is also appropriate for probe-based memories. However, experimentally the successful writing of amorphous bits using scanning electrical probes has not been widely reported. In light of this a second approach has been studied, that of writing crystalline bits in an amorphous starting matrix, with subsequent erasure by re-amorphization. With conventional phase-change materials, such as continuous films of Ge 2 Sb 2 Te 5 , this approach invariably leads to the formation of a crystalline 'halo' surrounding the erased (re-amorphized) region, with severe adverse consequences on the achievable density. Suppression of the 'halo' was achieved using patterned media or slow-growth phase-change media, with the latter seemingly more viable.