Nucleation and grain growth in as deposited and ion implanted GeTe thin films

Mio, Antonio Massimiliano; Carria, E.; D’Arrigo, Giuseppe; Gibilisco, S.; Miritello, M.; Grimaldi, M. G.; Rimini, E.

doi:10.1016/j.jnoncrysol.2011.02.042

Cited by 21 publications

(17 citation statements)

References 25 publications

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“…Thus, the decrease in the effective activation energy for crystallization of GeTe observed for increasing deposition temperatures is primarily due to a reduction in the activation energy for nucleation. Similar activation energies for nucleation and growth of films deposited at room temperature have been reported elsewhere using a different technique [10,30]. Films deposited at room temperature experience a higher effective quench rate as compared to films deposited at higher temperatures [31].…”

Section: Resultssupporting

confidence: 72%

“…4 a The local effective activation energy E c as a function of the fraction transformed a for films prepared at various deposition temperatures and b activation energies for nucleation and growth as a function of the deposition temperature homopolar Te-Te bonds in the as-deposited state. It is known that homopolar Te-Te bonds are forbidden in the crystalline structure [10]. It has therefore been suggested that the presence of these homopolar Te-Te bonds might retard the crystallization process [9].…”

Section: Resultsmentioning

confidence: 99%

“…The operation of these devices strongly depends on the crystallization temperatures and crystallization rates of the materials, and therefore, a detailed understanding of factors that influence the kinetics of crystallization is critical. Studies of amorphous Ge 2 Sb 2 Te 5 and GeTe films prepared using different methods, such as sputtering, melt-quenching, and ion-irradiation, have been carried out [9,10]. The local order of these amorphous films has been examined using Raman spectroscopy and was found to be significantly different [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…Studies of amorphous Ge 2 Sb 2 Te 5 and GeTe films prepared using different methods, such as sputtering, melt-quenching, and ion-irradiation, have been carried out [9,10]. The local order of these amorphous films has been examined using Raman spectroscopy and was found to be significantly different [9,10]. These differences were found to correlate with differences in crystallization temperatures [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…The local order of these amorphous films has been examined using Raman spectroscopy and was found to be significantly different [9,10]. These differences were found to correlate with differences in crystallization temperatures [9,10].…”

Section: Introductionmentioning

confidence: 99%

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Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

et al. 2015

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The speed at which phase change memory devices can operate depends strongly on the crystallization kinetics of the amorphous phase. To better understand factors that affect the crystallization rate, we have investigated crystallization of GeTe films as a function of their deposition temperatures and deposition rates, using X-ray synchrotron radiation and Raman spectroscopy. As-deposited films were found to be fully amorphous under all conditions, even though films deposited at higher temperatures and lower rates experienced lower effective quench rates. Non-isothermal transformation curves show that the apparent crystallization temperature of GeTe films decreases with increasing deposition temperature and decreasing deposition rate. It was found that this correlates with a decrease in the activation energy for nucleation (calculated using Kissinger's analysis), while the activation energy for crystal growth remained unaffected. From Raman spectroscopy measurements, it was found that increasing the deposition temperature or decreasing the deposition rate, and therefore the effective quench rate, reduces the number of homopolar Te-Te bonds and thereby reduces the barrier to crystal nucleation.

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Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

et al. 2015

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Ultra‐Thin Switchable Absorbers Based on Lossy Phase‐Change Materials

Heßler

Bente

Wuttig

et al. 2021

Advanced Optical Materials

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a wavelength causes destructive interference of light and the light is absorbed at the metal surface.Along with current trends to eversmaller, more versatile devices, thin and reconfigurable infrared absorbers which do not require cumbersome nanofabrication are desirable, for example, to fabricate ultra-thin, effective light detectors. This is especially true for the mid-infrared spectral range, where optical imaging devices are important for many technological applications in key areas like thermography, surveillance, automotive safety, and astronomy. [8] It has been shown that ultra-thin absorbers can consist of just an imperfect conductor as a reflector and a very thin, lossy dielectric as the absorbing film because of non-trivial phase shifts at the interfaces. [13] Originally, the absorber functionalities are fixed after fabrication, limiting their application range. To achieve more versatile absorbers, research has been directed towards realizing tunable absorption functionality. [8,[14][15][16][17][18][19][20][21][22] Phase-change materials (PCMs) are especially interesting for this because they offer non-volatile tuning (in contrast to the volatile tuning with transparent conducting oxides or phasetransition materials) by switching between their amorphous and crystalline structural phases whose optical properties differ significantly, because of a unique bonding mechanism, referred to as metavalent bonding. [23][24][25][26] They can be switched between their phases by thermal, [27] electrical, [28] or optical heating [29] on time-scales down to a few nanoseconds [30] and they have already been successfully commercialized in products like re-writable DVDs [29] and PC-RAM. [31] Crystallization leads to an approximately twofold increase of the refractive index in the infrared spectral range for many PCMs [32,33] like Ge 2 Sb 2 Te 5 and its stoichiometric neighbors Ge 3 Sb 2 Te 6 and Ge 8 Sb 2 Te 11 . In addition, these PCMs feature low losses in the infrared, which makes them suitable for many nanophotonics applications [34][35][36] like waveguides, [37,38] photonic memory, [39,40] polaritonics, [41][42][43][44] tunable metasurfaces, [45][46][47][48][49][50][51][52][53] and tunable metasurface absorbers. [8,14,18,[54][55][56][57] But the same low-loss optical properties become disadvantageous for constructing ultra-thin absorbers with thicknesses well beyond the quarterwavelength limit. While their use is still viable in the visible and near-infrared spectral range [58][59][60] where they have significant optical losses, they are no longer suitable at infrared frequencies. Absorbersfor infrared light are important optical components in key areas like biosensing, infrared imaging, and (thermal) light emission, with special need for thin and reconfigurable devices. Here, the authors demonstrate ultra-thin, switchable infrared absorbers based on thin layers of chalcogenide phase-change materials (PCMs) with high optical contrast between a lossless amorphous and an exceptionally lossy crystalline phase (Ge 3 Sb ...

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Nanosecond‐scale time‐resolved electron imaging during laser crystallization of GeTe

Santala

Reed

Raoux³

et al. 2012

Physica Status Solidi (b)

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Laser crystallization of amorphous phase change materials (PCMs) occurs on the nanosecond scale, during which it is challenging to probe the details of microstructural development experimentally. In this study, in situ laser‐induced crystallization of amorphous GeTe thin films was imaged with transmission electron microscopy with 15‐ns time resolution. These data provide insight into the crystallization process of PCMs during laser crystallization. The initial results allow us to begin to develop a detailed picture of the crystallization process when high spatial and temporal temperature gradients exist. Differences in the nucleation rate may be distinguished within the laser‐affected area and changes in the microstructure before crystallization suggest the occurrence of melting of the amorphous phase at the laser energy used. The amorphous melting temperature is estimated based on the thermodynamic data available.

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Nucleation and grain growth in as deposited and ion implanted GeTe thin films

Cited by 21 publications

References 25 publications

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

Impact of deposition conditions on the crystallization kinetics of amorphous GeTe films

Ultra‐Thin Switchable Absorbers Based on Lossy Phase‐Change Materials

Nanosecond‐scale time‐resolved electron imaging during laser crystallization of GeTe

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