Nanoscale Electrolytic Switching in Phase‐Change Chalcogenide Films

Pandian, Ramanathaswamy; Kooi, Bart J.; Palasantzas, G.; Hosson, J.Th.M. De; Pauza, Andrew

doi:10.1002/adma.200700904

Cited by 50 publications

(54 citation statements)

References 34 publications

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“…A detailed investigation of the influence of electron beam on the crystal growth is subject of a separate publication. 38 In order to entirely avoid such an influence in the present experiments, crystallization was carried out without electron beam exposure for fixed time intervals at elevated temperature. After each interval, the sample is cooled to nearly room temperature ͑below 30°C͒ for TEM measurements, i.e., the measurements of nucleation and growth were made in discrete heating and cooling steps unlike in our previous studies, 35,36 where it was done in a more or less continuous manner.…”

Section: Methodsmentioning

confidence: 99%

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Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Pandian

Kooi

Hosson

et al. 2006

Journal of Applied Physics

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Isothermal crystallization of doped Sb x Te fast-growth phase-change films, with and without capping layers, was investigated using transmission electron microscopy, which provided direct and quantitative information on nucleation and growth processes separately. Two types of amorphous dielectric layers, ZnS -SiO 2 and GeCrN, were used for sandwiching the Sb x Te films to form typical trilayer stacks, which are the active part in applications. The nucleation and growth parameters of Sb x Te films were found to be influenced by the dielectric capping layers. The crystal growth rate is temperature dependent and it reduces when the film is sandwiched between the dielectric layers. The reduction in growth rate differs with the capping layer type. The capping layer influence on the growth rate is pronounced at lower temperatures ϳ160°C, but tends to vanish at higher temperatures ϳ200°C. The activation energy for crystal growth is 2.4± 0.3 eV for an uncapped film and it increases ϳ40% when the capping layers, GeCrN or ZnS -SiO 2 , are added. A temperature and time dependent nucleation rate is found and it is accelerated ϳ1.7 times by GeCrN layers, whereas it is retarded ϳ5 times by ZnS -SiO 2 layers. The activation energy for crystal nucleation is 6.1± 0.4 eV for an uncapped film and it is not noticeably altered by the capping layers. These variations observed in the crystallization kinetics are attributed to variations in interface energy between the phase-change film and the capping layers or vacuum and the confinement effect by the capping layers on the phase-change film.

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Section: Methodsmentioning

confidence: 99%

“…37 In the following we will disregard this effect, but we will address it in Ref. 38 where also the influence of electron beam of the TEM ͑that is now absent for the present measurements͒ on the growth velocity is analyzed in detail.…”

Section: A Growth Propertiesmentioning

confidence: 99%

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Pandian

Kooi

Hosson

et al. 2006

Journal of Applied Physics

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“…Many research groups have reported various types of recording methods based on scanning tunneling microscopy (STM) [4,5], atomic force microscopy (AFM) [6][7][8][9][10], and scanning near-field optical microscopy (SNOM) [11,12], etc. Moreover, in order to increase the data transfer rate, parallel data processing using a probe array, i.e.…”

Section: Introductionmentioning

confidence: 99%

Formation of a Flat Conductive Polymer Film Using Template-Stripped Gold (TSG) Surface and Surface-Graft Polymerization for Scanning Multiprobe Data Storage

Yoshida

Ono

Esashi

2008

e-J. Surf. Sci. Nanotechnol.

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A thin conductive polymer recording medium with angstrom-scale surface roughness has been formed on template-stripped gold (TSG) surface by surface-graft polymerization for scanning multiprobe data storage. A gold film is deposited on a mica plate, which is bonded onto the silicon substrate with a gold film using gold-gold direct bonding technique. By removing the mica plate, gold surface with the angstrom-scale surface roughness is formed. A conductive polymer film as a recording medium is deposited on the TSG surface by the surface-graft polymerization. As a result, the polymer film with small roughness is obtained. Thus, the use of the TSG surface is efficient way to form the flat conductive polymer film. Finally, reversible electrical modification on the polymer film is demonstrated using atomic force microscopy. These results show the possibility that this formation method of the conductive polymer film provides rewritable recording media with small roughness for scanning multiprobe high-density data storage.

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“…ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114 19. Downloaded on 2015-06-28 to IP…”

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confidence: 98%

Switching Power Reduction in Phase Change Memory Cell Using CVD Ge[sub 2]Sb[sub 2]Te[sub 5] and Ultrathin TiO[sub 2] Films

Choi

et al. 2009

J. Electrochem. Soc.

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Phase change memory cells were fabricated using plasma-enhanced cyclic chemical-vapor-deposited Ge 2 Sb 2 Te 5 ͑GST͒ thin films deposited on 300 nm diameter TiN/W contact plugs formed in a SiO 2 layer. A 2, 4, and 8 nm thick atomic deposited TiO 2 layer was interposed between the GST and underlayer containing the contact plug. The necessary reset current and power decreased with increasing the TiO 2 interlayer thickness. Adoption of the optimum thickness ͑4 nm͒ TiO 2 layer decreased the necessary reset power to ϳ45% of the cell without the TiO 2 layer. This was attributed mainly to the effective heat insulation by the 4 nm thick TiO 2 layer. The structural investigation and electrothermal simulation results for the fabricated cells showed a good match between the electrical performance and phase changed volume, which can explain the improvement in switching parameters of the proper TiO 2 layer interposed cell.Phase change random access memory ͑PCRAM͒ has attracted considerable interest recently for highly integrated nonvolatile memory ͑NVM͒ devices. 1-3 There are many major advantages of the PCRAM compared with conventional NVM, such as the NAND or NOR-type flash memory. In contrast to NAND flash, perfect random access during data writing and reading is possible, which allows effective cell use and rapid operation. Although NOR flash allows random access operation, the tunneling of electrons between the channel and floating gate to write and erase the data results in the need for a long writing time ͑from a few microseconds to milliseconds͒ and high voltage ͑15-20 V͒ in both NAND and NOR flashes. This is not the case for the PCRAM due to the rapid switching speed of phase change ͑PC͒ materials ͑Ͻ100 ns͒, typically Ge 2 Sb 2 Te 5 ͑GST͒, under the low applied voltage, Ͻ3 V. A reasonably small cell size of the PCRAM ͑6F 2 , where F is the minimum feature size͒ in a conventional 1 transistor-1 resistor configuration is another merit of this device although it is still slightly larger than that of NAND ͑ϳ5F 2 and ϳ10F 2 for the NAND and NOR, respectively͒. However, there are several drawbacks of the current PCRAMs. The high level of reset current ͑I reset ϳ 0.5 mA͒ needed to switch the GST material from a crystalline to amorphous state ͑reset process͒ has been the major obstacle to the further scaling of PCRAM because of the limited on-current drive capability of the cell transistor ͑Ͻ1 mA m −1 ͒. 4 Several methods have been used in an attempt to overcome this problem including doping of GST, 3-7 confining the GST into a contact plug, 8-10 adopting an ultrathin interface thermal barrier layer ͑UTB͒ of Ta 2 O 5 ͑Ref. 11͒, or TiO 2 , 12 and adopting diodes as the selection device that generally offers a larger drive current than the field-effect transistor. 3 Among them, adopting a UTB appears to be an effective method for reducing I reset , even though other methods also showed some improvements. It was suggested that the oxide layer with a lower thermal conductivity suppresses the heat loss to the metal plug and impro...

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Nanoscale Electrolytic Switching in Phase‐Change Chalcogenide Films

Cited by 50 publications

References 34 publications

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Influence of capping layers on the crystallization of doped SbxTe fast-growth phase-change films

Formation of a Flat Conductive Polymer Film Using Template-Stripped Gold (TSG) Surface and Surface-Graft Polymerization for Scanning Multiprobe Data Storage

Switching Power Reduction in Phase Change Memory Cell Using CVD Ge[sub 2]Sb[sub 2]Te[sub 5] and Ultrathin TiO[sub 2] Films

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