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Optimization of equipment structure and process conditions is essential to obtain thin films with the required properties, such as film thickness, trapped charge density, leakage current, and memory characteristics, that ensure reliability of the corresponding device. In this study, we fabricated metal–insulator–semiconductor (MIS) structure capacitors using HfO2 thin films separately deposited by remote plasma (RP) atomic layer deposition (ALD) and direct-plasma (DP) ALD and determined the optimal process temperature by measuring the leakage current and breakdown strength as functions of process temperature. Additionally, we analyzed the effects of the plasma application method on the charge trapping properties of HfO2 thin films and properties of the interface between Si and HfO2. Subsequently, we synthesized charge-trapping memory (CTM) devices utilizing the deposited thin films as charge-trapping layers (CTLs) and evaluated their memory properties. The results indicated excellent memory window characteristics of the RP-HfO2 MIS capacitors compared to those of the DP-HfO2 MIS capacitors. Moreover, the memory characteristics of the RP-HfO2 CTM devices were outstanding as compared to those of the DP-HfO2 CTM devices. In conclusion, the methodology proposed herein can be useful for future implementations of multiple levels of charge-storage nonvolatile memories or synaptic devices that require many states. [ABSTRACT FROM AUTHOR]

Hf0.5Zr0.5O2 (HZO) thin film exhibits ferroelectric properties and is presumed to be suitable for use in next-generation memory devices because of its compatibility with the complementary metal–oxide–semiconductor (CMOS) process. This study examined the physical and electrical properties of HZO thin films deposited by two plasma-enhanced atomic layer deposition (PEALD) methods— direct plasma atomic layer deposition (DPALD) and remote plasma atomic layer deposition (RPALD)—and the effects of plasma application on the properties of HZO thin films. The initial conditions for HZO thin film deposition, depending on the RPALD deposition temperature, were established based on previous research on HZO thin films deposited by the DPALD method. The results show that as the measurement temperature increases, the electric properties of DPALD HZO quickly deteriorate; however, the RPALD HZO thin film exhibited excellent fatigue endurance at a measurement temperature of 60 °C or less. HZO thin films deposited by the DPALD and RPALD methods exhibited relatively good remanent polarization and fatigue endurance, respectively. These results confirm the applicability of the HZO thin films deposited by the RPALD method as ferroelectric memory devices. [ABSTRACT FROM AUTHOR]

Core‐shell structure in Cd‐Zn‐Se quantum dots (QDs) precipitated in the silicate glass matrix by continuous wave laser (λ = 532 nm) were demonstrated using transmission electron microscopy (TEM) and local electrode atom probe (LEAP) tomography. TEM images of the QDs in glasses after 60 min of irradiation at 9 W/cm2 show two portions with different contrasts, and diameters of 5.97 and 22.49 nm, respectively; 3D elemental distribution in these glasses from LEAP tomography shows areas of high Zn concentration near the CdSe QDs. Iso‐concentration images obtained using visualization software show that Cd‐rich clusters were not completely covered by the Zn‐rich shells in the glass after 15 min irradiation that resulted emission due to the surface defects of CdSe QDs. As the irradiation time increased to 60 min, the Zn‐rich cluster gradually surrounded the Cd‐rich core to form shells that eliminated the surface defects. During laser irradiation, CdSe QDs precipitated first due to the high degree of supersaturation of Cd and Se followed by the sequential incorporation of Zn on the Cd‐rich QDs forming shells. [ABSTRACT FROM AUTHOR]

CdSe QDs with Cd1−xZnxSe shell structures were precipitated inside silicate glasses by continuous‐wave laser irradiation (λ = 532 nm) without any heat‐treatment process. Emission from the surface defects (λ ≈ 620 nm) was quenched significantly and the lifetimes of the band‐edge emission was increased. During the laser irradiation, Zn ions were gradually incorporated into the outer region of CdSe QDs to form Cd1−xZnxSe (0.76 ≤ x ≤ 0.8) alloy shells. [ABSTRACT FROM AUTHOR]

The influence of Nd2O3 addition on the precipitation kinetics of lead chalcogenide (PbS) quantum dots ( QDs) in silicate glasses was investigated. Energy dispersive X-ray spectroscopy ( EDS) indicated that the Nd3+ ions are preferentially located inside the PbS QDs rather than in the glass matrix. Changes in diameter ( D) of PbS QDs exhibited smaller time dependencies (i.e., D≈ t0.270-0.286) than that predicted by the classical Lifshitz-Slyozov-Wagner ( LSW) theory. This is due to the limited concentrations of Pb2+ and S2− ions and the large diffusion distance inside the glass matrix. In addition, extended X-ray absorption fine structure ( EXAFS) results indicated that the formation of PbS QDs was retarded due to the presence of Nd2O3 in the glasses, as the large NdO x polyhedra interrupt the diffusion of Pb2+ and S2− ions. We believe that these Nd3+ ions are primarily located in PbS QDs in the form of Nd-O clusters, and that the PbS QDs are built on top of these clusters. [ABSTRACT FROM AUTHOR]

The influence of Nd3+ ions was investigated on the precipitation and optical properties of PbS quantum dots ( QDs) inside silicate glasses. The diameters of the PbS QDs decreased as the concentration of Nd3+ in the glass increased as evidenced by blue shifts in the absorption and photoluminescence spectra. Electron energy loss spectroscopy shows that Nd3+ ions exist preferentially inside the PbS nanocrystals rather than in the glass matrix. We postulate that Nd-O clusters are preserved during heat treatment and serve as nucleation sites for PbS crystals. No change in the local bonding scheme of the Nd3+ ions was observed following heat treatment. [ABSTRACT FROM AUTHOR]

Abstract: Efficiency enhancement of a multicrystalline silicon solar cell using down-conversion of Tm3+ and Yb3+ doped silicate glasses was investigated. Na2O–CaO–SiO2 glasses doped with Tm3+ or Tm3+ and Yb3+ were prepared. Distributed Bragg Reflector (DBR) coatings were sputtered on the glass surface to control the transmission and reflection of the desired portion of the solar spectrum. These were placed on a multicrystalline silicon solar cell in combination with a solar spectrum simulator. The efficiency of solar cell with Tm3+ or Tm3+ and Yb3+ doped glasses increased compared to as-prepared glass without rare-earth addition. The efficiency of solar cell with rare earth doped glasses was re-measured three times with same samples, and the real efficiency enhancement can be proved. The potentials, limitations and future perspectives of rare-earth doped glasses with DBR structure on the efficiencies of PV modules were discussed. [Copyright &y& Elsevier]