Thermomechanical properties and mechanical stresses of Ge2Sb2Te5 films in phase-change random access memory

Park, Il-Mok; Jung, Jung-Kyu; Ryu, Sang-Ouk; Choi, Kyu-Jeong; Yu, Byoung–Gon; Park, Young-Bae; Han, Seung Min; Joo, Young‐Chang

doi:10.1016/j.tsf.2008.08.194

Cited by 104 publications

(69 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For ultrafast processes such as those in the current experiment, the electron and lattice subsystems are not initially in equilibrium, leading to two independent contributions (and two different subsystem temperatures) to lattice expansion as exemplified by the electronic and lattice Grüneisen parameters, respectively [28]. The more than a factor of 4 increase in the thermal expansion coefficient α L over the published value [29] of 1.74 × 10 −5 K −1 found in the current fitting may reflect the contributions of the electronic Grüneisen parameter to the induced stress in the film. As the system can only expand along the z direction, an increase of up to a factor of 3 in α L might be anticipated due to the decrease in dimensionality, but the factor of 4 found here suggests additional contributions from electronic excitation effects [5].…”

Section: Discussionmentioning

confidence: 72%

Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

et al. 2014

View full text Add to dashboard Cite

Coherent phonons (CPs) generated by laser pulses on the femtosecond scale have been proposed as a means to achieve ultrafast, nonthermal switching in phase-change materials such as Ge 2 Sb 2 Te 5 (GST). Here we use ultrafast optical pump pulses to induce coherent acoustic phonons and stroboscopically measure the corresponding lattice distortions in GST using 100-ps x-ray pulses from the European Synchrotron Radiation Facility (ESRF) storage ring. A linear-chain model provides a good description of the observed changes in the diffraction signal; however, the magnitudes of the measured shifts are too large to be explained by thermal effects alone, implying the presence of excited-state effects in addition to temperature-driven expansion. The information on the movement of atoms during the excitation process can lead to greater insight into the possibilities of using CP-induced phase transitions in GST.

show abstract

Section: Discussionmentioning

confidence: 72%

Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

et al. 2014

View full text Add to dashboard Cite

show abstract

“…GST materials are also leading candidates for computer random access memory (PC-RAM) [17][18][19] and are expected to provide non-volatile memory in future low-energy electronic devices. The phase change in PCRAMs is initiated by resistive heating, and the state is monitored by measuring the resistivity [20].…”

Section: Introductionmentioning

confidence: 99%

Tuning electronic properties of graphene heterostructures by amorphous-to-crystalline phase transitions

2016

View full text Add to dashboard Cite

The remarkable ability of phase change materials (PCM) to switch between amorphous and crystalline states on a nanosecond time scale could provide new opportunities for graphene engineering. We have used density functional calculations to investigate the structures and electronic properties of heterostructures of thin amorphous and crystalline films of the PCM GeTe (16Å thick) and Ge2Sb2Te5 (20Å) between graphene layers. The interaction between graphene and PCM is very weak, charge transfer is negligible, and the structures of the chalcogenide films differ little from those of bulk phases. A crystalline GeTe (111) layer induces a band gap opening of 80 meV at the Dirac point. This effect is absent for the amorphous film, but the Fermi energy shifts down along the Dirac cone by −60 meV. Ge2Sb2Te5 shows similar features, although inherent disorder in the crystalline rocksalt structure reduces the contrast in band structure from that in the amorphous structure. These features originate in charge polarization within the crystalline films, which show electromechanical response (piezoelectricity) upon compression, and show that the electronic properties of graphene structures can be tuned by inducing ultra-fast structural transitions within the chalcogenide layers. Graphene can also be used to manipulate the structural state of the PCM layer and its electronic and optical properties.

show abstract

“…with specific heat C, linear expansion coefficient b, band gap E g , and photon energy E. For C $ 10 6 J/m 3 K, b $ 10 À5 K À1 , and ðE À E g Þ $ 1 eV, 14,28,29 the electronic and thermal contributions are equal and opposite for jdE g =dPj $ 0:03 eV/GPa. This is on the order of previously measured results.…”

mentioning

confidence: 99%

Ultrafast sub-threshold photo-induced response in crystalline and amorphous GeSbTe thin films

Shu

Chatzakis

Kuo

et al. 2013

Applied Physics Letters

View full text Add to dashboard Cite

Pump-probe optical reflectivity and terahertz transmission measurements have been used to investigate time resolved sub-threshold photo-induced effects in crystalline and amorphous GeSbTe films at MHz repetition rates. The reflectivity in both phases exhibits long-lived modulations consistent with the sign of the changes that occur upon switching but of smaller magnitude. These can be understood by the generation of acoustic strains with the crystalline phase response dominated by thermal effects and the amorphous phase response associated with electronically induced changes. Evidence for a photo-induced distortion is observed in the amorphous phase which develops homogeneously within the excited region on few-picosecond time scales.

show abstract

Thermomechanical properties and mechanical stresses of Ge2Sb2Te5 films in phase-change random access memory

Cited by 104 publications

References 19 publications

Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

Tuning electronic properties of graphene heterostructures by amorphous-to-crystalline phase transitions

Ultrafast sub-threshold photo-induced response in crystalline and amorphous GeSbTe thin films

Contact Info

Product

Resources

About