Dy2O3 Films Research Articles

Co-60 gamma radiation influences on the electrochemical, physical and electrical characteristics rare-earth dysprosium oxide (Dy2O3)

Dysprosium Oxide (Dy2O3) gate dielectric layers were deposited by Electron-Beam evaporation onto p-Si (100) wafers. The effects of gamma irradiation on the physical, electrochemical, and electrical properties of Dy2O3/p-Si thin films were investigated in detail. The evolutions on the crystallographic and morphologic characteristics of the films under gamma irradiation were analyzed by X-ray diffraction (XRD) and Atomic Force Microscopy (AFM), respectively; while irradiation effects on the electrochemistry of the films were characterized by X-ray photoelectron spectroscopy (XPS). Furthermore, variations on the electrical characteristics of Dy2O3/p-Si thin films were also specified by Capacitance-Voltage (C–V) and Conductance-Voltage (G/ω-V) measurements. No significant changes on the crystallographic orientation were observed after gamma irradiation exposures. However, the grain size of the films was increased slightly due to the local heating aggregated the smaller grains into a bigger cluster. In addition, the surface roughness was increased after irradiation indicating that deforms the films’ surface morphology. The XPS analysis revealed that electrochemically two different phases exist in the virgin Dy2O3/p-Si thin films. These phases are Dysprosium sub-Oxide (DyxOy) and oxygen deficient in Dy2O3 films. After irradiation exposures, oxygen incorporation, vacancy, and interstitial defects formation were observed in the electrochemical characteristics of the films. On the other hand, the capacitance curves exhibit kinks in the region between depletion and accumulation due to the presence of the intermixing phases of Dy2O3 films. The capacitance of samples significantly increased with the increasing dose, which are correlated with the generated interface state density and/or improvement of dielectric characteristics of Dy2O3 owing to oxygen diffusion.

Annealing-induced evolution in interface stability and electrical performance of sputtering-driven rare-earth-based gate oxides

Annealing temperature-dependent ultrathin Dy2O3 gate dielectric films, grown on Si substrates by reactive sputtering, were characterized in terms of structural, optical and electrical properties using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), UV–Vis transmission spectroscopy and electrical measurements of Dy2O3/Si gate stack. Additionally, the thickness of the interfacial SiO2 layer during the deposition and annealing process has been calculated using the Si 2p XPS spectra to exclude its influence on the electrical parameter of Dy2O3 films. XPS analyses for all the samples have shown the abrupt growth of the Dy-silicate for 700°C-annealed sample, which is identified as the primary reason for the dramatic reduction in its electrical performance. In addition, optimized Dy2O3 sample with annealed temperature at 600 °C exhibits the lowest equivalent oxide thickness of 1.6 nm, the highest dielectric constant 16.8, the lower leakage current density 4.45 × 10−8 A/cm2 and the lower frequency dispersion of 6.21%. Based on the experimental analysis, the optimized annealing temperature has been obtained to achieve Dy2O3 gate dielectric thin films as deposition of high-k with high-quality on Si substrates.

Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films grown by atomic layer deposition

Dysprosium oxide and dysprosium-oxide-doped titanium oxide thin films were grown by atomic layer deposition on silicon substrates. For depositing dysprosium and titanium oxides Dy(thd)3-O3 and TiCl4-O3 were used as precursors combinations. Appropriate parameters for Dy(thd)3-O3 growth process were obtained by using a quartz crystal microbalance system. The Dy2O3 films were deposited on planar substrates and on three-dimensional substrates with aspect ratio 1:20. The Dy/Ti ratio of Dy2O3-doped TiO2 films deposited on a planar silicon substrate ranged from 0.04 to 0.06. Magnetometry studies revealed that saturation of magnetization could not be observed in planar Dy2O3 films, but it was observable in Dy2O3 films on 3D substrates and in doped TiO2 films with a Dy/Ti atomic ratio of 0.06. The latter films exhibited saturation magnetization 10−6 A cm2 and coercivity 11 kA/m at room temperature.

The temperature dependence on the electrical properties of dysprosium oxide deposited on p-Si substrate

In this paper, we make a study on the effect of films thickness on the electrical properties of the dielectric Dy2O3 deposited on p-Si substrate. The electrical characteristics of Al/Dy2O3/p-Si hetero-structure were investigated in the temperature range of 270–420K. The conductance and capacitance-frequency measurements were performed as a function of temperature. The results indicate that the electrical properties are strongly dependent on both temperature and frequency. It was found that both C and G are quite sensitive to frequency at relatively low frequencies. The AC conductance characteristic was found to obey Jonscher universal power law. Also, the Dy2O3 films exhibited a thermally activated conductance, i.e., G(T)=G0 exp(−Ea/kBT), over a considerable temperature range. Activation energy is deduced from the variation of conductance with temperature as it decreases from 172 to 82meV whenever the thickness of Dy2O3 film increases. Besides, the dielectric properties of Al/Dy2O3/p-Si hetero-structure are studied by means of complex impedance spectroscopy. The frequency-dependence of the dielectric constant ε׳ and dielectric loss ε″ of the elaborated samples is subsequently investigated at different temperatures. Experimental results reveal that the aforementioned parameters have strong frequency dependence. The obtained values of ε׳ and ε″ show increments with decreasing frequency. However, increasing frequency levels cause an increase in the AC electrical conductivity. In order to gain an insight into the electric nature of the samples, the Cole–Cole diagrams are also investigated at different temperatures.

Physical and Electrical Properties of Dy2O3 and Dy2TiO5 Metal Oxide–High-κ Oxide–Silicon-Type Nonvolatile Memory Devices

In this paper, we compare the physical and electrical properties of metal oxide–high-κ oxide–silicon (MOHOS)-type devices using Dy2O3 and Dy2TiO5 films as charge-trapping layers. X-ray diffraction and x-ray photoelectron spectroscopy revealed the structural and compositional features of these films after annealing at various temperatures. MOHOS memory devices incorporating the Dy2TiO5 trapping layer that had been annealed at 800°C exhibited a larger memory window of ~2.91 V (measured at a sweep voltage range of ±9 V), higher flatband voltage shift of 2 V (programming voltage at 9 V for 0.1 s), and smaller charge loss of ~10% (measured at room temperature after 104 s), relative to those of the systems that had been subjected to other annealing conditions. This result suggests that the Dy2TiO5 film featuring a higher dielectric constant as well as a thinner silicate layer provides a higher probability of charge carrier trapping and deeper electron trapping levels. In addition, the centroid of trapped charge in the Dy2TiO5 layer was extracted by the constant current stress method and compared with that of the Dy2O3 layer.

Unipolar resistive switching behavior in Dy2O3 films for nonvolatile memory applications

In this article, we report the forming-free resistive switching behavior of a Ru/Dy2O3/TaN memory device incorporating a Dy2O3 thin film fabricated entirely through processing at room temperature. We used X-ray diffraction, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy to investigate the structural and chemical features of the Dy2O3 film. The dominant conduction mechanisms in the low- and high-resistance states were ohmic behavior and Poole–Frenkel emission, respectively. The Ru/Dy2O3/TaN memory device exhibited a high resistance ratio and provided nondestructive readout and reliable data retention. This memory device has a great potential for application in nonvolatile resistive switching memory.

Response to “Comment on ‘Forming-free resistive switching in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature’” [Appl. Phys. Lett. 100, 076101 (2012)

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Comment on “Forming-free resistive switching behavior in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature” [Appl. Phys. Lett. 99, 113509 (2011)

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Metal–Oxide–High-$k$ -Oxide–Silicon Memory Device Using a Ti-Doped $\hbox{Dy}_{2}\hbox{O}_{3}$ Charge-Trapping Layer and $\hbox{Al}_{2}\hbox{O}_{3}$ Blocking Layer

In this paper, we propose Al/SiO2/Dy2O3/ SiO2/ Si, Al/SiO2/DyTixOy/SiO2/Si, and Al/Al2O3/DyTixOy/SiO2/Si as charge-trapping memory devices incorporating high-k Dy2O3 and Ti-doped Dy2O3 films as charge-trapping layers, and SiO2 and Al2O3 films as blocking layers. The Al/Al2O3/DyTix Oy/ SiO2/Si memory device exhibited a larger memory window of ~4.5 V (measured at a sweep voltage range of ±9 V), a smaller charge loss of ~20% (measured time up to 106s and at 85°C), and better endurance (program/erase cycles up to 104) than other devices. These results suggest higher probability for trapping the charge carrier due to the Ti content in the Dy2O3 film, which produce a high dielectric constant and suppress the formation of the Dy-silicate layer, and create a deep trap level in the DyTixOy film.

Forming-free resistive switching behavior in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature

In this study, we reported the forming-free resistive switching behavior in the Ru/RE2O3/TaN (RE = Nd, Dy, and Er) memory devices using thin Nd2O3, Dy2O3, and Er2O3 films fabricated with full room temperature process. The dominant conduction mechanisms of the Ru/RE2O3/TaN devices in the low-resistance state and high-resistance state are Ohmic behavior. The Ru/Dy2O3/TaN memory device exhibited high resistance ratio, nondestructive readout, reliable data retention, and good endurance. Ru/Dy2O3/TaN memory device has a great potential for the application in nonvolatile resistive switching memory.

Epitaxial growth of Dy2O3 films on SrTiO3(001) substrates by molecular beam epitaxy

Epitaxial Dy2O3 thin films are grown on SrTiO3(001) substrates by molecular beam epitaxy. Structural, morphological, and interfacial properties of the Dy2O3 film are investigated by in situ reflection high-energy electron diffraction (RHEED), ex situ x-ray diffraction (XRD), atomic force microscopy, and cross-sectional transmission electron microscopy (TEM). RHEED patterns and XRD spectra show that the Dy2O3 film is grown epitaxially in a cubic phase with a (001) orientation. The surface of the film is smooth with a rms roughness of 4 Å. The TEM image shows that the Dy2O3 film is crystalline with an abrupt interface between the film and substrate without any indication of a chemical reaction or interdiffusion occurring at the interface.

Epitaxial Dy2O3 Thin Films Grown on Ge(100) Substrates by Molecular Beam Epitaxy

AbstractDysprosium oxide (Dy2O3) films are grown epitaxially on high mobility Ge(100) substrates by molecular beam epitaxy system. Reflection high energy electron diffraction patterns and X-ray diffraction spectra show that single crystalline cubic Dy2O3 films are formed on Ge(100) substrates. The epitaxial-relationship is identified as Dy2O3 (110)║Ge(100) and Dy2O3 [001]║Ge[011]. Atomic force microscopy results show that the surface of the Dy2O3 film is uniform, flat and smooth with root mean square surface roughness of about 4.6Å. X-ray photoelectron spectroscopy including depth profiles confirms the composition of the films being close to Dy2O3. TEM measurements reveal a sharp, crystalline interface between the oxide and Ge.

Nanostructured Dy2O3 films: An XPS Investigation

The present investigation is devoted to the X-ray photoelectron spectroscopy (XPS) analysis of the main core levels (C 1s, O 1s, Dy 4d, Dy 3d) of a representative dysprosium(III) oxide thin film. The specimen was grown on Si(100) at 500 °C by metal organic chemical vapor deposition (MOCVD) starting from Dy((iPrN)2CNMe2)3 in an N2/O2 atmosphere. The above route yielded uniform and homogeneous nanostructured Dy2O3 films characterized by a remarkable reactivity towards atmospheric CO2 and H2O, resulting in the surface co-presence of dysprosium carbonates/bicarbonates and hydroxides. The most relevant spectral features are presented and discussed.

Molecular beam epitaxy of Sm2O3, Dy2O3, and Ho2O3 on Si (111)

We report on the epitaxial deposition of Sm2O3, Dy2O3, and Ho2O3 films on Si (111) substrates as progress towards developing a predictive model for gate oxide selection. To date, films have been characterized by reflection high-energy electron diffraction, x-ray diffraction (XRD), and x-ray photoemission spectroscopy (XPS). In the case of Sm2O3, difficulty was encountered in achieving the growth of phase pure films; growth of the desired bixbyite oxide phase was accompanied by significant amounts of monoclinic oxide as detected by XRD. Dy2O3 and Ho2O3 films can be produced free of unwanted phases when deposited using a background pressure of 1×10−6torr O2∕O3 and a substrate temperature between 425 and 550°C. Dy2O3 films with an x-ray peak width of 0.6° in ω were obtained. XPS studies of the Dy2O3∕Si interface are in progress, and verify the phase purity of the films.

Investigation of the surface structure of dysprosium and praseodymium oxide-based polycrystalline films sensitive to ozone and vapors of ethanol and methanol

The surface of dysprosium and praseodymium oxide-based films is investigated by atomic-force microscopy and electron probe X-ray microanalysis. The electrical properties of the films are determined. It is shown that the electrical conductivity of the Dy2O3 films can be substantially changed by introducing dopants of zirconium and praseodymium oxides into the initial solution used for synthesizing the films (in particular, the ZrO2-based dopant increases the electrical conductivity of the Dy2O3 film and the PrOx-based dopant affects the conductivity in a complex way). The temperature dependence of the film sensitivity to ozone and vapors of ethanol and methanol is studied.

Effects of Post Dielectric Deposition and Post Metallization Annealing Processes on Metal/Dy2O3/Si(100) Diode Characteristics

Ultra-high vacuum annealing was investigated for Dy2O3 films deposited on Si(100) substrates. The leakage current of the Dy2O3 films deposited at room temperature (RT) was found to be decreased without any increase of the equivalent oxide thickness (EOT) by the in-situ vacuum annealing method compared to that of the conventional rapid thermal annealing (RTA) in O2. The negative flat-band voltage (VFB) shift observed after the in-situ vacuum annealing process was suppressed by increasing the deposition temperature of Dy2O3 on chemically oxidized Si from RT to 250°C. The EOT of 1.1 nm with the leakage current of 0.29 A/cm2 (@VFB+1 V) was obtained for the Dy2O3 film after the air-brake and vacuum annealing, and the EOT of 0.63 nm with 4 A/cm2 (@VFB+1 V) was achieved for the Dy2O3 film with the TaN gate electrode after the post metallization annealing (PMA).