Editing Phase-change memory (section)

{{Short description|Novel computer memory type}}
{{Memory types}}
'''Phase-change memory''' (also known as '''PCM''', '''PCME''', '''PRAM''', '''PCRAM''', '''OUM''' ('''ovonic unified memory''') and '''C-RAM''' or '''CRAM''' ('''chalcogenide RAM''')) is a type of [[non-volatile random-access memory]]. PRAMs exploit the unique behaviour of [[chalcogenide glass]]. In PCM, heat produced by the passage of an [[electric current]] through a [[heating element]] generally made of [[titanium nitride]] is used to either quickly heat and [[Quenching|quench]] the glass, making it [[amorphous solid|amorphous]], or to hold it in its crystallization temperature range for some time, thereby switching it to a [[crystal]]line state.<ref>{{Cite journal|last1=Le Gallo|first1=Manuel|last2=Sebastian|first2=Abu|date=2020-03-30|title=An overview of phase-change memory device physics|journal=Journal of Physics D: Applied Physics|language=en|volume=53|issue=21|pages=213002|doi=10.1088/1361-6463/ab7794|bibcode=2020JPhD...53u3002L |s2cid=213023359 |issn=0022-3727|doi-access=free}}</ref> PCM also has the ability to achieve a number of distinct intermediary states, thereby having the ability to hold multiple [[bit]]s in a single cell,<ref>{{Cite journal|last1=Burr|first1=Geoffrey W.|last2=BrightSky|first2=Matthew J.|last3=Sebastian|first3=Abu|last4=Cheng|first4=Huai-Yu|last5=Wu|first5=Jau-Yi|last6=Kim|first6=Sangbum|last7=Sosa|first7=Norma E.|last8=Papandreou|first8=Nikolaos|last9=Lung|first9=Hsiang-Lan|last10=Pozidis|first10=Haralampos|last11=Eleftheriou|first11=Evangelos|date=June 2016|title=Recent Progress in Phase-Change Memory Technology|url=https://ieeexplore.ieee.org/document/7453199|journal=IEEE Journal on Emerging and Selected Topics in Circuits and Systems|volume=6|issue=2|pages=146–162|doi=10.1109/JETCAS.2016.2547718|bibcode=2016IJEST...6..146B |s2cid=26729693 |issn=2156-3357|url-access=subscription}}</ref> but the difficulties in programming cells in this way has prevented these capabilities from being implemented in other technologies (most notably [[flash memory]]) with the same capability.

Recent research on PCM has been directed towards attempting to find viable material alternatives to the [[phase-change material]] [[GeSbTe|Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>]] (GST), with mixed success. Other research has focused on the development of a [[Germanium|Ge]][[Tellurium|Te]]–[[Antimony|Sb]]<sub>2</sub>Te<sub>3</sub> [[superlattice]] to achieve non-thermal [[Phase transition|phase changes]] by changing the co-ordination state of the germanium atoms with a [[laser]] pulse. This new Interfacial Phase-Change Memory (IPCM) has had many successes and continues to be the site of much active research.<ref>{{cite journal|display-authors=4|last=Simpson|first=R.E.|author2=P. Fons|author3=A. V. Kolobov|author4=T. Fukaya|author5=M. Krbal|author6=T. Yagi|author7=J. Tominaga|name-list-style=amp|title=Interfacial phase-change memory|journal=Nature Nanotechnology|date=July 2011|doi=10.1038/nnano.2011.96|pmid=21725305|volume=6|issue=8|pages=501–5|bibcode=2011NatNa...6..501S|s2cid=6684244}}</ref>

[[Leon Chua]] has argued that all two-terminal [[Non-volatile memory|non-volatile-memory]] devices, including PCM, should be considered [[memristor]]s.<ref name="chua11">{{citation |last=Chua |first=L. O. |date=2011 |title=Resistance switching memories are memristors |journal=Applied Physics A |volume=102 |issue=4 |pages=765–783 |doi=10.1007/s00339-011-6264-9 |bibcode=2011ApPhA.102..765C|doi-access=free }}</ref> [[R. Stanley Williams|Stan Williams]] of [[HP Labs]] has also argued that PCM should be considered a memristor.<ref name="Mellor2011">{{Citation |last=Mellor |first=Chris |date=10 October 2011|title=HP and Hynix to produce the memristor goods by 2013|url=https://www.theregister.co.uk/2011/10/10/memristor_in_18_months/ |work=The Register |access-date=2012-03-07}}</ref> However, this terminology has been challenged, and the potential applicability of memristor theory to any physically realizable device is open to question.<ref name="Meuffels_2012">{{cite arXiv |last1=Meuffels |first1=P. |last2=Soni |first2=R. |date=2012 |title=Fundamental Issues and Problems in the Realization of Memristors |eprint=1207.7319 |class=cond-mat.mes-hall }}</ref><ref name="DiVentra_2013">{{cite journal|last=Di Ventra|first=Massimiliano|author2=Pershin, Yuriy V.|title=On the physical properties of memristive, memcapacitive and meminductive systems|journal=Nanotechnology|date=2013|volume=24|issue=25|doi=10.1088/0957-4484/24/25/255201|arxiv = 1302.7063 |bibcode = 2013Nanot..24y5201D|pmid=23708238|page=255201|citeseerx=10.1.1.745.8657|s2cid=14892809}}</ref>