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Makino K, Kato K, Saito Y, Fons P, Kolobov AV, Tominaga J, Nakano T, Nakajima M. Terahertz generation measurements of multilayered GeTe-Sb 2Te 3 phase change materials. OPTICS LETTERS 2019; 44:1355-1358. [PMID: 30874649 DOI: 10.1364/ol.44.001355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 02/08/2019] [Indexed: 06/09/2023]
Abstract
Multilayered structures of GeTe and Sb2Te3 phase change material, also referred to as interfacial phase change memory (iPCM), provide superior performance for nonvolatile electrical memory technology in which the atomically controlled structure plays an important role in memory operation. Here, we report on terahertz (THz) wave generation measurements. Three- and 20-layer iPCM samples were irradiated with a femtosecond laser, and the generated THz radiation was observed. The emitted THz pulse was found to be always p polarized independent of the polarization of the excitation pulse. Based on the polarization dependence as well as the flip of the THz field from photoexcited Sb2Te3 and Bi2Te3, the THz emission process can be attributed to the surge current flow due to the built-in surface depletion layer formed in p-type semiconducting iPCM materials.
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Makino K, Kuromiya S, Takano K, Kato K, Nakajima M, Saito Y, Tominaga J, Iida H, Kinoshita M, Nakano T. THz Pulse Detection by Multilayered GeTe/Sb 2Te 3. ACS APPLIED MATERIALS & INTERFACES 2016; 8:32408-32413. [PMID: 27933830 DOI: 10.1021/acsami.6b11418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We proposed and demonstrated terahertz (THz) pulse detection by means of multilayered GeTe/Sb2Te3 phase-change memory materials that are also known as a multilayer topological insulator-normal insulator (MTN) system. THz time-domain spectroscopy measurement was performed for MTN films with different multilayer repetitions as well as a conventional as-grown Ge-Te-Sb (GST) alloy film. It was found that MTNs absorb THz waves and that the absorption coefficient depends on the number of layers, while the as-grown GST alloy film was almost transparent for THz waves. Simple MTN-based THz detection devices were fabricated, and the THz-induced change in the current signal was measured when a DC bias voltage was applied between the electrodes. We confirmed that irradiation of THz pulse causes a decrease in the resistance of the MTNs. This result indicates that our devices are capable of THz detection.
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Affiliation(s)
- Kotaro Makino
- Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8565, Japan
| | - Shota Kuromiya
- Institute of Laser Engineering, Osaka University , Suita, Osaka 565-0871, Japan
| | - Keisuke Takano
- Institute of Laser Engineering, Osaka University , Suita, Osaka 565-0871, Japan
| | - Kosaku Kato
- Institute of Laser Engineering, Osaka University , Suita, Osaka 565-0871, Japan
| | - Makoto Nakajima
- Institute of Laser Engineering, Osaka University , Suita, Osaka 565-0871, Japan
| | - Yuta Saito
- Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8565, Japan
| | - Junji Tominaga
- Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8565, Japan
| | - Hitoshi Iida
- National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8563, Japan
| | - Moto Kinoshita
- National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8563, Japan
| | - Takashi Nakano
- Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8565, Japan
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Morphology and Electric Conductance Change Induced by Voltage Pulse Excitation in (GeTe)2/Sb2Te3 Superlattices. Sci Rep 2016; 6:33223. [PMID: 27618797 PMCID: PMC5020502 DOI: 10.1038/srep33223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 08/23/2016] [Indexed: 11/08/2022] Open
Abstract
Chalcogenide superlattice (SL) phase-change memory materials are leading candidates for non-volatile, energy-efficient electric memory where the electric conductance switching is caused by the atom repositioning in the constituent layers. Here, we study the time evolution of the electric conductance in [(GeTe)2/(Sb2Te3)1]4 SLs upon the application of an external pulsed electric field by analysing the structural and electrical responses of the SL films with scanning probe microscopy (SPM) and scanning probe lithography (SPL). At a low pulse voltage (1.6–2.3 V), a conductance switching delay of a few seconds was observed in some SL areas, where the switch to the high conductance state (HCS) is accompanied with an SL expansion under the strong electric field of the SPM probe. At a high pulse voltage (2.5–3.0 V), the HCS current was unstable and decayed in a few seconds; this is ascribed to the degradation of the HCS crystal phase under excessive heating. The reversible conductance change under a pulse voltage of opposite polarity emphasised the role of the electric field in the phase-transition mechanism.
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