Crystallization process of Sb-Te alloy films for optical storage

Fujimori, Susumu; Yagi, Shunsuke; Yamazaki, Hiroki; Funakoshi, Nobuhiro

doi:10.1063/1.341908

Cited by 105 publications

(31 citation statements)

References 8 publications

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“…If chemical control prevails over cortical influence on the respiratory controller, as typically occurs during sleep, patients become apneic until Pa C O 2 rises again above the apnea threshold. Thus, the alternating pattern of apnea and hyperpnea continues due to oscillations of the Pa C O 2 around the apnea threshold [52,53]. This periodic respiratory over- and undershoot causes additional sympathetic stimulation in patients who are already sympathetically stimulated through their heart failure [54].…”

Section: Pathophysiology Of Csrmentioning

confidence: 99%

Cheyne-Stokes Respiration in Patients with Heart Failure: Prevalence, Causes, Consequences and Treatments

Brack¹,

Randerath

Bloch

2011

Respiration

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Cheyne-Stokes respiration (CSR) is characterized by a pattern of cyclic oscillations of tidal volume and respiratory rate with periods of hyperpnea alternating with hypopnea or apnea in patients with heart failure. CSR harms the failing heart through intermittent hypoxia brought about by apnea and hypopnea and recurrent sympathetic surges. CSR impairs the quality of life and increases cardiac mortality in patients with heart failure. Thus, CSR should actively be pursued in patients with severe heart failure. When CSR persists despite optimal therapy of heart failure, noninvasive adaptive servoventilation is currently the most promising treatment.

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Section: Pathophysiology Of Csrmentioning

confidence: 99%

Cheyne-Stokes Respiration in Patients with Heart Failure: Prevalence, Causes, Consequences and Treatments

Brack¹,

Randerath

Bloch

2011

Respiration

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“…2 In addition to the well known GST composition, the Sb:Te binary compositions are also known phase change materials. 5 The appreciation of bismuth's mechanism in Sb:Te compounds could aid the understanding in the somewhat more complex Bi doped ternary systems. The Sb 2 Te phase shows a wide compositional tolerance with Sb content ranging from 63 to 81 at.…”

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confidence: 99%

Reduction in crystallization time of Sb:Te films through addition of Bi

Simpson

Hewak

Fons³

et al. 2008

Applied Physics Letters

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The electrical, optical, and phase change properties of bismuth doped Sb 8 Te 2 films have been characterized. Thin films of the material, with up to 15 at. % percent Bi, have been synthesized; amorphous films were stable at room temperature with a Bi concentration of up to 13 at. %. The effect of Bi on the phase change properties of the film is shown to reduce the crystallization time by an order of magnitude while the crystallization activation energy reduction is minimal; 0.2 eV. Over the last 30 years, 1 phase change materials have been extensively investigated for optical data storage applications. Phase change recording is based on the reversible switching between the crystalline and amorphous states. The rate that data can be erased and directly overwritten is reliant on the crystallization time of the material; thus, understanding the effect of compositional variations on the crystallization times of these materials is of key importance.The effect of Bi doping, in the well researched Ge 2 Sb 2 Te 5 ͑GST͒ phase change alloy, has been reported by a number of groups. [2][3][4] Experimental results demonstrate that the use of Bi as a dopant could play an important role in the demonstration of improved data storage materials. When doped in GST, Bi is known to reduce the transition temperatures without affecting the crystal structure or its lattice parameters. 2In addition to the well known GST composition, the Sb:Te binary compositions are also known phase change materials. 5The appreciation of bismuth's mechanism in Sb:Te compounds could aid the understanding in the somewhat more complex Bi doped ternary systems. The Sb 2 Te phase shows a wide compositional tolerance with Sb content ranging from 63 to 81 at. %. 6 In this work, samples containing 80% Sb have been doped with Bi; close to the maximum Sb concentration at which the Sb 2 Te phase is formed. Since this crystal can form over a wide Sb compositional range, it is anticipated that it will show some acceptance of the Bi atom. The crystallization, optical, and electrical properties have been investigated.The Bi content was varied between 0 and 15 at. % by attaching pure Bi pieces to a Sb 8 Te 2 sputtering target. Sputtering was performed in an argon atmosphere, controlled at 0.5 Pa, with a rf power of 100 W. Films, with thickness of 100 nm, were deposited onto Si and SiO 2 substrates. The film composition was measured by x-ray fluorescence spectroscopy using a Rigaku RIX 2100 system. The crystallization temperature and its activation energy were measured by monitoring the reflection as a function of temperature, using a Linkam microscope furnace in conjunction with a broad visible source and a monochromator-detector setup. Measurements of the crystallization temperature were made at heating rates of 5, 10, 15, 20, and 25°C min −1 in an Ar atmosphere. These heating rates are many orders of magnitude lower than that of laser or joule heating. However, for the purpose of comparing samples measured in the same fashion, these heating rates were deemed suffici...

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“…The crystallization of amorphous chalcogenide films has been proven by other researchers to be a process involving nucleation and growth. 16,22,30) The secondary phase precipitated in the early stage can be expected to enhance the heterogeneous nucleation but the higher crystallization temperature of the AIST film reveals that crystallization may be more difficult for the movement of Ag and In atoms in the amorphous matrix. It is believed that the formation of a small amount of AgSbTe 2 phase slightly affected the activation energy and thus, crystallization rate of the amorphous AIST film.…”

Section: Electrical Properties Of Aist and St Filmsmentioning

confidence: 99%

“…The nucleation and growth of -Sb phase can be easy because the literature has reported that there is little volume fraction change associated with the formation of a nucleus for crystallization, and less strain and surface energy need to be overcome when a nucleus grows from the amorphous matrix. [30][31][32] The crystallization rates of amorphous AIST and ST films can be expected to be small and be close to each other because the same major phase (-Sb) is formed. The similar activation energy obtained in Fig.…”

Section: Electrical Properties Of Aist and St Filmsmentioning

confidence: 99%

Variation of Microstructure and Electrical Conductivity of Amorphous AgInSbTe and SbTe Films during Crystallization

2007

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Two kinds of chalcogenide films with similar Sb/Te atomic ratios, AgInSbTe (AIST) and SbTe (ST) were deposited on alkali-free glass using the RF sputtering method. The microstructure characteristics of both ST and AIST films were demonstrated to correlate with the electrical properties. TEM observation and GI-XRD profiles revealed that the structures of as-deposited AIST and ST films were amorphous characteristics. The sheet resistance of the as-deposited AIST films was twice as high as that of ST films and the effect of Ag and In additives was proposed. After annealing at 523 K for 1 h, the sheet resistance of both chalcogenide films decreased by four orders of magnitude due to crystallizations and the sheet resistance of crystallized AIST film was still twice as large as that of crystallized ST film. DSC measurement was used to determine the crystallization temperature of AIST films as 476 K and that of ST films as 445 K. The activation energies of crystallization were determined using Kissinger's method, and 0.94 eV and 0.84 eV were obtained for AIST and ST films, respectively. TEM observations showed that AgSbTe 2 phase exists in the AIST film after heat treatment in addition to -Sb phase. No indium compounds were discovered in the AIST film by the energy dispersive spectroscopy (EDS) and XRD measurements.

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Crystallization process of Sb-Te alloy films for optical storage

Cited by 105 publications

References 8 publications

Cheyne-Stokes Respiration in Patients with Heart Failure: Prevalence, Causes, Consequences and Treatments

Cheyne-Stokes Respiration in Patients with Heart Failure: Prevalence, Causes, Consequences and Treatments

Reduction in crystallization time of Sb:Te films through addition of Bi

Variation of Microstructure and Electrical Conductivity of Amorphous AgInSbTe and SbTe Films during Crystallization

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