This paper delves into the application of the short-wave infrared (SWIR) region, with a focus on the synthesis and optical characteristics of silver sulfide (Ag2S) nanostructures. SWIR offers advantages such as reduced damage to biological tissues and enhanced optical transparency, making it valuable across various domains. The study introduces three distinct synthesis methods, each showcasing the ability to obtain nanostructures with improved optical properties. These research findings open up the possibility of providing tailored solutions in detection, imaging, and other applications by controlling the size and ligands of Ag2S nanoparticles. This paper provides new insights into the utilization of Ag2S in the SWIR region, which is expected to foster advancements in future technologies.
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Enhancing the Sensitivity and Spectral Selectivity of Colloidal Quantum Dot Infrared Photodetectors Using Metasurfaces Min Jeong Kim, Tae Won Nam Journal of Electrical and Electronic Materials.2026; 39(4): 340. CrossRef
This work reports the electrical characteristics of and temperature distribution in chalcogenide phase change memory (PCM) devices that have a self-aligned structure. GST (Ge-Sb-Te) chalcogenide alloy films were formed in a self-aligned manner by interdiffusion between sputter-deposited Ge and Sb2Te3 films during thermal annealing. A transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) analysis demonstrated that the local composition of the GST alloy differed significantly and that a Ge2Sb2Te5 intermediate layer was formed near the Ge/Sb2Te3 interface. The programming current and threshold switching voltage of the PCM device were much smaller than those of a control device; this implies that a phase transition occurred only in the Ge2Sb2Te5 intermediate layer and not in the entire thickness of the GST alloy. It was confirmed by computer simulation, that the localized phase transition and heat loss suppression of the GST alloy promoted a temperature rise in the PCM device.
In this work, we evaluated the structural, electrical and optical properties of Ge8Sb2Te11 and Cu-doped Ge8Sb2Te11 thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of 100~400℃ using a furnace in an N2 atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature (Tc) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap (Eop) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance(Rs) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large Rs in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage (Vth) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped Ge8Sb2Te11 thin film is a good candidate for PRAM.
Thermal and structural stability in the glass transition region of chalcogenide glasses has been investigated in terms of thermodynamics for application to various optoelectronic devices. In this study, the compositions of GexSb20Se80-x (x = 10, 15, 20, 25, and 30) were selected to investigate the glass stability according to germanium ratios. The chalcogenide bulks were fabricated by using a traditional melt-quenching method. Thin films were deposited by a thermal evaporation system, maintaining the deposition ratio of 3~5 A in order to have uniformity. The thermal and structural properties were measured by a differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The DSC analysis provided thermal parameters and theoretical glass region stabilities. The XRD analysis supported the theoretical stabilities because of where the crystallization peak data occurred.
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Characteristics of Heavy Metal Oxide Glasses in BaO-GeO2-La2O3-ZnO-Sb2O3 System for Infrared Lens Sang-Jin Park, Bok-Hyun Oh, Sang-Jin Lee Korean Journal of Materials Research.2023; 33(10): 414. CrossRef
In this study, Ge2Sb2Te5 and Ge8Sb2Te11 were used as an insulator layer to fabricate ReRAM devices. The resistance change is correlated to the appearance or disappearance of a conductivity filament at the surface of the GeSbTe layer. Changes in the electrical properties of ITO/GeSbTe/Ag devices were measured using a I-V-L measurement system. As a result, compared to the ITO/Ge8Sb2Te11/Ag device, this ITO/Ge2Sb2Te5/Ag ReRAM device exhibits highly uniform bipolar resistive switching characteristics, such as the operating voltages, and the resistance values.
We evaluated the structural, electrical and optical properties of tungsten (W)-doped Ge8Sb2Te11 thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve thermal stability. 200 mm thick Ge8Sb2Te11 and W-doped Ge8Sb2Te11 films were deposited on p-type Si (100) and glass substrates using a magnetron co-sputtering system at room temperature. The fabricated films were annealed in a furnace in the 0~400℃ temperature range. The structural properties were analyzed using X-ray diffraction (X`pert PRO, Phillips). The results showed increased crystallization temperature (Tc) leading to thermal stability in the amorphous state. The optical properties were analyzed using an UV-Vis-IR spectrophotometer (Shimadzu, U-3501, range : 300~3,000 nm). The results showed an increase in the crystalline material optical energy band gap (Eop) and an increase in the Eop difference (△Eop). This is a good effect to reduce memory device noise. The electrical properties were analyzed using a 4-point probe (CNT-series). This showed increased sheet resistance (Rs), which reduces programming current in the memory device.
The dielectric thin films applied to multi-colored semitransparent thin film solar cells have been extensively studied. In this work, we prepared GeSbTe and GeTe chalcogenide thin films using magnetron sputtering, and investigated their optical and phase-change properties to replace the dielectric films. The changes of surface morphology, sheet resistance, and X-ray diffraction of the Te-based chalcogenide films support the fact that the amorphous stability of GeTe films is superior to that of GeSbTe films. While both amorphous GeSbTe and GeTe films thinner than 30 nm have optical transparency between 5% and 60%, GeTe films transmit more visible light than GeSbTe films. It is confirmed by computer simulation that the color of semitransparent silicon thin film solar cells can be adjusted with the addition of GeSbTe or GeTe films. Since it is possible to adjust the contrast of the solar cells by exploiting the phase-change property, the two kinds of chalcogenide films are anticipated to be used as an optical layer in semitransparent solar cells.
The resistive switching characteristics of resistive random access memory (ReRAM) based onamorphous Ge0.5Se0.5 thin films have been demonstrated by using Ti/Ag nanocrystals/Ge0.5Se0.5/Ptstructure. Ag nanocrystals (Ag NCs) were spread on the amorphous Ge0.5Se0.5 thin film and they playedthe role of metal ions source. As a result, comparing the conventional Ag/Ge0.5Se0.5/Pt structure, thisTi/Ag NCs/Ge0.5Se0.5/Pt ReRAM device exhibits the highly uniform bipolar resistive switching (BRS)characteristics, such as the operating voltages, and the resistance values. At the same time, a stable DCendurance(> 100 cycles), and the excellent data retention (> 104 sec) properties were found from theTi/Ag NCs/Ge0.5Se0.5/Pt structured ReRAM device.
Aspheric lenses used in the thermal imaging are typically fabricated using expensive single-crystal materials (Ge and ZnS, etc.) by the costly single point diamond turning (SPDT) process. As a potential solution to reduce cost, compression molding method using chalcogenide glass has been attracted to fabricate IR optic. Thermal deformation of a molded lens should be compensated to fabricate chalcogenide aspheric lens with form accuracy of the submicron-order. The thermal deformation phenomenon of molded lens was analyzed ant then compensation using mold iteration process is followed to fabricate the high accuracy optic. Consequently, it is obvious that compensation of thermal deformation is critical and useful enough to be adopted to fabricate the lens by molding method.
The chalcogenide glass has superior optical properties in IR region transmittances. We have determined the composition of GeSbSe chalcogenide glass for the application of good IR lenses, resulting in the composite rate of Ge19Sb23Se58. The optical, structural, thermal and physical properties were measured by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Differential scanning calorimeter (DSC), X-ray computed tomography (X-ray CT) respectively. The fabrication of the chalcogenide glass lens for infrared optics applications was proposed using a diamond turning machining technology which is known as the suitable ways for the production cost reduction and the accurate fabrication process control.
For phase transition method, good record sensitivity, low heat radiation, fast crystallization and hi-resolution are essential. Also, a retention time is very important part for phase-transition. In our past papers, we chose composition of Ge1Se1Te2 material to use a Se factor which has good optical sensitivity than conventional Sb. Sb/Ge-Se-Te thin films are fabricated and irradiated with UV light source to investigate a reversible phase change by Sb-doped condition. Because of Sb atoms, the Sb inserted sample showed better performance than conventional one. We should note that this novel one showed another possibility for phase-change random access memory.
In this study, we have investigated the holographic grating formation on Ag-doped amorphous As-Ge-Se-S thin films. The dependence of diffraction efficiency as afunction of Ag layer thickness has been investigated in this amorphous chalcogenide films. Holographic gratings was formed using [P:P] polarized Diode Pumped Solid State laser (DPSS, 532.0 nm). The diffraction efficiency was obtained by +1st order intensity. The results were shown that the diffraction efficiency of Ag/AsGeSeS double layer thin films for the Ag thickness, the maximum grating diffraction efficiency using 60 nm Ag layer is 0.96%.
Resistance-change Random Access Memory(ReRAM) memory, which utilizes electrochemical control of metal in thin films of solid electrolyte, shows great promise as a future solid state memory. The technology utilizes the electrochemical formation and removal of metallic pathways in thin films of solid electrolyte. Key attributes are low voltage and current operation, excellent scalability, and a simple fabrication sequence. In this work, we investigated the nature of thin films formed by photo doping of Ag+ ions into chalcogenide materials for use in solid electrolyte of Resistance-change RAM devices and switching characteristics according to field-effect.
In this study, we synthesized the chalcogenide glass(Ge19Sb23Se58) for infrared optics by melt-quenching method and verified the effect of cooling condition on the glass properties. The structural and optical properties of the glass were analyzed by XRD, FT-IR and SEM image. The glass synthesized under the cooling temperature of 980℃ shows transmittance of 58% at 8∼12 ㎛, which was decreased as the cooling temperature was decreased. In addition, thermal and hardness also were measured. From the analysis results, we ascertained the feasibility as a molding materials for infrared optics.
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