Submicron Nonvolatile Memory Cell Based on Reversible Phase Transition in Chalcogenide Glasses

Nakayama, Keiichi I.; Kojima, Kazuhiko; Hayakawa, Fumihito; Imai, Yoshihiko; Kitagawa, Akio; Suzuki, Masakuni

doi:10.1143/jjap.39.6157

Cited by 68 publications

(35 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the electronic contribution in Ge 2 Sb 2 Te 5 forms a relatively small part of the overall thermal conductivity, as can be estimated via the Weidemann-Franz relationship 21 using an activationtype temperature dependence of electrical conductivity. 22,23 Indeed, thermal-conductivity measurements of other amorphous chalcogenides showed little more than a few tens of percent increase in thermal conductivity for temperatures ranging from ambient right up to the crystallization temperature. 24,25 The assumption of a constant thermal conductivity over the temperature ranges of interest in this work is not therefore overly restrictive, and a value of 0.4 W/m K at the transition temperature ͑lying between the amorphous and crystalline values͒ is used.…”

Section: Temperature Gradientmentioning

confidence: 99%

A slope-theory approach to electrical probe recording on phase-change media

Aziz

Wright

2005

Journal of Applied Physics

View full text Add to dashboard Cite

A theoretical approach to predicting the spatial extent of the amorphous to crystalline transition region during the probe recording process on phase-change storage media is presented. The extent of this transition region determines the ultimate achievable linear density for data storage using phase-change materials. The approach has parallels with the slope theory used to find magnetic transition lengths in magnetic recording, and shows that the amorphous to crystalline transition length can be minimized by reducing the thickness of the phase-change layer, by minimizing lateral heat flow, and by maximizing the ratio of the activation energy for crystallization to the transition temperature E c / T t .

show abstract

Section: Temperature Gradientmentioning

confidence: 99%

A slope-theory approach to electrical probe recording on phase-change media

Aziz

Wright

2005

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…In recent years, the main focus of phase-change data-storage research returned to resistance switching. So-called chalcogenide or phase-change random access memory (CRAM/PRAM) and ovonic unified memory (OUM) based on the phase-dependent resistance switching are currently under intense investigations, [5][6][7][8][9][10][11][12][13] because they show great promise as next-generation nonvolatile solid-state memory replacing flash memory. In certain chalcogenides a special phenomenon of polaritydependent resistance switching (induced by an electric field) has been identified.…”

mentioning

confidence: 99%

Nanoscale Electrolytic Switching in Phase‐Change Chalcogenide Films

et al. 2007

View full text Add to dashboard Cite

This Communication presents the important finding that certain chalcogenide materials, well-known from rewritable optical recording, allow resistive memory states that are a combination of two electrically-induced (reversible) switching processes, i.e., an actual amorphous-crystalline phase transformation and a (electrolytic) polarity-dependent resistance change. Nanometer-sized crystalline marks were written electrically in amorphous Ge 2 Sb 2+x Te 5 films using atomic force microscopy (AFM), and their resistance was found to depend on the polarity of the applied voltage with a resistance difference of three orders of magnitude. However, no contrast in current has been detected between the crystalline higherresistance state and the surrounding amorphous phase. This resistance switching is reversible for bias voltages well below the threshold voltage required to induce the phase transformation. The switching mechanism is attributed to the solidstate electrolytic behavior due to the presence of excess Sb in the films. Our results render exciting technological opportunities for data storage and encryption by combining both switching concepts.Following his seminal work in 1968, [1] Ovshinsky demonstrated in chalcogenide alloys a fast reversible transformation between amorphous and crystalline phases induced by electrical or optical (laser) pulses. [2][3][4] The two phases exhibited clear contrast in electrical and optical properties and, hence, these materials were suggested for binary data-storage applications. However, it took considerable time before rewritable optical compact discs (CD) and digital versatile discs (DVD) based on these findings came to the market. In recent years, the main focus of phase-change data-storage research returned to resistance switching. So-called chalcogenide or phase-change random access memory (CRAM/PRAM) and ovonic unified memory (OUM) based on the phase-dependent resistance switching are currently under intense investigations, [5][6][7][8][9][10][11][12][13] because they show great promise as next-generation nonvolatile solid-state memory replacing flash memory. In certain chalcogenides a special phenomenon of polaritydependent resistance switching (induced by an electric field) has been identified. [14][15][16][17][18][19] This is related to the solid-state electrolytic character and high ionic conductivities of chalcogenides, and hence is called ionic/electrolytic switching. For one polarity, the chalcogenide medium is electrically conductive by forming conducting filamentary pathways between electrodes, whereas for the reverse polarity it becomes relatively insulative or at least less conductive because of rupture of the previously formed electrical pathways. Memory elements (or structures) based on this switching have been demonstrated in some Ag-saturated chalcogenides including Ag-S, [14,15] AgGe-Se, [16,17] Ag-Ge-Te, [18] and Ag-In-Sb-Te. [19] This switching seems more attractive for applications than phase-dependent switching, because i) it can be performed at lower volta...

show abstract

“…The temperature dependence of the sheet resistance in the amorphous phase follows an activation-type relation 6 . To estimate the activation barrier for transport E a , given in the temperature dependence of the conductivity ,…”

Section: Resultsmentioning

confidence: 99%

Chalcogenide Alloys as a Basis for New Non-Volatile Random Access Memories

Dieker¹,

Noerenberg²,

Steimer³

et al. 2006

Functional Properties of Nanostructured Materials

View full text Add to dashboard Cite

Abstract. In the past decades chalcogenide alloys have been successfully employed for rewritable optical data storage. Beside the optical contrast upon phase change from the amorphous to the crystalline state utilized in optical data storage devices, chalcogenide alloys show an even more pronounced change in their electronic properties, namely their resistivity 1 . This resistivity change is the basis of a new purely electronic memory device the so-called phase change random access memory (PCRAM). We present the electrical properties of one candidate material, namely Ge 2 Sb 2 Te 5 , and also demonstrate in a first experiment the switching operation of a single cell.

show abstract

Submicron Nonvolatile Memory Cell Based on Reversible Phase Transition in Chalcogenide Glasses

Cited by 68 publications

References 10 publications

A slope-theory approach to electrical probe recording on phase-change media

A slope-theory approach to electrical probe recording on phase-change media

Nanoscale Electrolytic Switching in Phase‐Change Chalcogenide Films

Chalcogenide Alloys as a Basis for New Non-Volatile Random Access Memories

Contact Info

Product

Resources

About