Optimization of Al2O3/ZrO2 nanolaminate structure for thin-film encapsulation of OLEDs

We report thin-film moisture barriers based on Al₂O₃/ZrO₂ nanolaminates grown by ALD for an encapsulation of OLEDs. In order to optimize the moisture-barrier performance of the nanolaminates, the most important factors affecting the performance were sought by measuring WVTR of the nanolaminates via an electrical Ca test. We found out that both the number of interfaces in the nanolaminates and the thickness of ZrO₂ in a unit layer were responsible for the performance. By optimizing the nanolaminate structure, the moisture-barrier performance was enhanced up to 350% from a single layer of the same thickness. The WVTR of 30-nm-thick optimized nanolaminate barrier was 2 × 10⁻⁴ g/(m² day) or less at ambient condition. A storage-lifetime measurement of an OLED with a 100-nm-thick encapsulation layer showed that it could exceed 70,000 h if stored at ambient condition.     

Hydrogen-assisted low-temperature plasma-enhanced chemical vapor deposition of thin film encapsulation layers for top-emission organic light-emitting diodes

In this work, we developed a single high-performance SiN_x encapsulation layer that can be directly integrated into organic devices by low-temperature plasma-enhanced chemical vapor deposition (PECVD). We investigated a hydrogen-assisted low-temperature PECVD process at a temperature of 80 °C. The thin film density improved with an increased hydrogen gas ratio, and the moisture permeability was less than 5 × 10⁻⁵ g/m²·day. To verify the stability of the PECVD process, we applied the SiN_x encapsulation layer directly to top-emitting organic light-emitting diodes. The results showed minor changes in the current-density–voltage characteristics after the PECVD process, as well as high reliability after a water dipping test.     

Low-cost supercritical CO2/H2O2 treatment on ITO anodes of fluorescent organic light-emitting diodes

A simple and cost-effective approach is proposed as an alternative to conventional oxygen plasma treatment to modify surface property of Indium tin oxide (ITO) anode of a fluorescent organic light-emitting diode (OLED). This was achieved by treating the ITO anode in supercritical CO₂ (SCCO₂) fluids with hydrogen peroxide (H₂O₂). The SCCO₂/H₂O₂ treatment yielded an ITO work function of 5.35 eV after 15 min treatment at 85 °C and 4000 psi, which was significant higher than 4.8 eV of the as-cleaned ITO surface and was slightly less than 5.5 eV of the ITO surface treated by oxygen plasma. The highest work function achieved was 5.55 eV after 45 min SCCO₂/H₂O₂ treatment. The SCCO₂/H₂O₂ treatment can be used to tailor the ITO work function through changing the operation pressure of the treatment. In addition, the correlated dependence of OLED performance on the ITO anodes with and without the treatments was investigated. The maximum power efficiency of 1.94 lm/W was obtained at 17.3 mA/cm² for the device with 15 min SCCO₂/H₂O₂ treatment at 4000 psi. This power efficiency was 19.3% and 33.8% higher than those of the oxygen plasma treatment and as-clean, respectively. The improvement in device efficiency by the SCCO₂/H₂O₂ treatments can be attributed to enhanced hole injection and balance in charge carriers due to increased work function and surface energy of the ITO anodes.     

原子层沉积方法制备低温多层Al2O3/TiO2复合封装薄膜的研究

原子层沉积(ALD)方法可以制备出高质量薄膜,被认为是可应用于柔性有机电致发光器件(OLED)最有发展前景的薄膜封装技术之一。本文采用原子层沉积(ALD)技术,在低温(80℃)下,研究了Al₂O₃及TiO₂薄膜的生长规律,通过钙膜水汽透过率(WVTR)、薄膜接触角测试等手段,研究了不同堆叠结构的多层Al₂O₃/TiO₂复合封装薄膜的水汽阻隔特性,其中5 nm/5 nm×8 dyads(重复堆叠次数)的Al₂O₃/TiO₂叠层结构薄膜的WVTR达到2.1×10^-5 g/m²/day。采用优化后的Al₂O₃/TiO₂叠层结构薄膜对OLED器件进行封装,实验发现封装后的OLED器件在高温高湿条件下展现了较好的寿命特性。     

Silica nanoparticle-embedded sol-gel organic/inorganic hybrid nanocomposite for transparent OLED encapsulation

We report a transparent moisture barrier coating fabricated with a silica nanoparticle-embedded organic/inorganic hybrid (S-H) nanocomposite. We used a photo-curable, cyclo-aliphatic epoxy based hybrid material (hyrimer) as the matrix and a solvent-less, monodisperse silica nanoparticles as the reinforcement responsible for creating tortuous diffusive path for moisture penetrants. The S-H nanocomposite barrier coating exhibits a single layer WVTR of 0.24 g/m² day (Ca-test) and an optical transparency of 90% in the visible range. The performance of the barrier coating was also verified in an OLED lifetime measurement test, in which an OLED encapsulated with an S-H nanocomposite barrier coating showed significantly extended lifetime.     

Layered Al2O3-TiO2 compositedielectric resonators

Aluminium oxide displays a very low tanδ at microwave frequencies. It also possesses a remarkably high thermal conductivity, ideal for heat dissipation in high power satellite filters. However, its temperature coefficient of the resonant frequency (τ_f) is approximately 60 ppm/K. It is shown that the application of a film of titanium oxide which has a T_f of opposite sign (45O ppm/K) produces a composite in which the τ_f can be tuned to be zero over a wide temperature range. The tanδ of the composite at zero T_f is 3.3×10⁵ (Q=30000) at room temperature and at 10 GHz     

Electrical and interfacial characteristics of nanolaminate (Al2O3/ZrO2/Al2O3) gate stack on fully depleted SiGe-on-insulator

The structural and electrical characteristics of a novel nanolaminate Al₂O₃/ZrO₂/Al₂O₃ high-k gate stack together with the interfacial layer (IL) formed on SiGe-on-insulator (SGOI) substrate have been investigated. A clear layered Al₂O₃ (2.5 nm)/ZrO₂ (4.5 nm)/Al₂O₃ (2.5 nm) structure and an IL (2.5 nm) are observed by high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy measurements indicate that the IL contains Al-silicate without Ge atom incorporation. A well-behaved C–V behavior with no hysteresis shows the absence of Ge pileup or Ge segregation at the gate stack/SiGe interface.     

Improved retention characteristic of charge-trapped flash device with sealing layer/Al2O3 or Al2O3/high-k stacked blocking layers

Although programming and erase speeds of charge trapping (CT) flash memory device are improved by using Al₂O₃ as blocking layer, its retention characteristic is still a main issue. CT flash memory device with Al₂O₃/high-k stacked blocking layer is proposed in this work to enhance data retention. Moreover, programming and erase speeds are slightly improved. In addition, sealing layer (SL), which is formed by an advanced clustered horizontal furnace between charge trapping layer and Al₂O₃ as one of the blocking layers is also studied. The retention characteristic is enhanced by SL approach due to lower gate leakage current with less defect. With the combination of SL and Al₂O₃/high-k stacked blocking layer approaches, retention property can be further improved.     

Single-frequency Ti:Al2O3 ring laser

Over 500 mW of single-frequency power has been obtained from a Ti:Al₂O₃ ring laser pumped by 10 W (all lines) from an argon ion laser. The ring laser can be tuned from 750 to 850 nm while maintaining more than 100 mW in single-frequency operation without realignment or a change of optics. The free-running frequency stability of the laser is 3 MHz. Thermal effects cause changes in the ring cavity parameters, limiting the output power. This ring laser has also been operated with an acoustooptic mode locker to obtain 200-ps mode-locked pulses at 250 MHz with nearly the same average power as in single-mode operation     

MgO-Y_2O_3对热压烧结Al_2O_3性能的影响

以高纯的硫酸铝氨分解的无定形Al2O3为原料,MgO-Y2O3为烧结助剂,在N2气氛下热压烧结制备Al2O3陶瓷。研究了烧结助剂掺量对Al2O3材料的相组成、显微结构、烧结性能、力学性能、热导率和介电性能的影响。结果表明:所制Al2O3陶瓷具有细晶的显微结构特征和超高的抗弯强度。随着MgO-Y2O3掺量的增加,晶粒尺寸、抗弯强度和热导率先增大后减小,而介电损耗则呈现先减小后增大的变化规律。当MgO和Y2O3掺量均为质量分数2%时,Al2O3陶瓷呈现为较佳的综合性能:抗弯强度达最大值为603 MPa,热导率为36.47 W.m–1.K–1,介电损耗低至6.32×10–4。     

High-density MIM capacitors using Al2O3 andAlTiOx dielectrics

We have investigated the electrical characteristics of Al₂ O₃ and AlTiO_x MIM capacitors from the IF (100 KHz) to RF (20 GHz) frequency range. Record high capacitance density of 0.5 and 1.0 μF/cm² are obtained for Al₂ O₃ and AlTiO_x MIM capacitors, respectively, and the fabrication process is compatible to existing VLSI backend integration. However, the AlTiO_x MIM capacitor has very large capacitance reduction at increasing frequencies. In contrast, good device integrity has been obtained for the Al₂O₃ MIM capacitor as evidenced from the small frequency dependence, low leakage current, good reliability, small temperature coefficient, and low loss tangent     

A Ti:Al2O3 master-oscillator/power-amplifiersystem

The authors have constructed a multistage Ti:Al₂O₃ master-oscillator/power-amplifier system which generates 115-ns, 0.38-J pulses at 800 nm. The system is tunable from 760 to 825 nm and has a repetition rate of 10 Hz. Measurements of the output pulse demonstrate near-diffraction-limited performance and a Fourier-transform-limited bandwidth of ~4 MHz     

Fabrication of tunable [Al2O3:Alucone] thin-film encapsulations for top-emitting organic light-emitting diodes with high performance optical and barrier properties

The optical and barrier properties of thin-film encapsulations (TFEs) for top-emitting organic light-emitting diodes (TEOLEDs) were investigated using TFEs fabricated by stacking multiple sets of inorganic–organic layers. The inorganic moisture barrier layers were prepared by atomic layer deposition (ALD) of Al₂O₃ using trimethylaluminum (TMA) and O₃ as precursors and are shown to be efficient barriers against gases and vapors. The organic alucone layers were produced by molecular layer deposition (MLD) using TMA and ethylene glycol as precursors. The [Al₂O₃:Alucone] ALD/MLD films were used because their adjustable inorganic–organic nanolaminate composition allows for the tuning of the optical properties, thereby enhancing their application potential for the design and fabrication of high performance light out-coupling structures for TEOLEDs. By carefully adjusting the relative thickness ratio of the inorganic–organic encapsulation materials, optimized light extraction was achieved and the films not only maintained their high moisture barrier strength but also showed excellent optical performance.     

Stack gate PZT/Al2O3 one transistorferroelectric memory

We have developed a single transistor ferroelectric memory using stack gate PZT/Al₂O₃ structure. For the same ~40 Å dielectric thickness, the PZT/Al₂O₃/Si gate dielectric has much better C-V characteristics and larger threshold voltage shift than those of PZT/SiO₂/Si. Besides, the ferroelectric MOSFET also shows a large output current difference between programmed on state and erased off state. The <100 us erase time is much faster than that of flash memory where the switching time is limited by erase time     

钛宝石的晶体生长与性能

本文采用提拉法生长出了高光学质量的Ti:Al2O3单晶,讨论了生长和退火工艺对晶体质量的影响。在室温条件下,14.8mm长的TiAl2O3激光棒,以35mJ的Nd:YAG倍频激光泵浦,在带有色散元件的激光腔中,获得了6.4mJ(780nm)激光输出,激光效率为18%。     

Distribution and generation of traps in SiO2/Al2O3 gate stacks

In this work we combine charge-pumping measurements with positive constant voltage stress to investigate trap generation in SiO₂/Al₂O₃ n-MOSFET. Trap density has been scanned either in energy or in position based on charge-pumping (CP) measurements performed under different operating conditions in terms of amplitude and frequency of the gate pulse. Our results have revealed that the traps are meanly localized shallow in energy level, deeper in spatial position and they are mostly generated near the Si/SiO₂ interface.     

Electrical measurements of voltage stressed Al2O3/GaAs MOSFET

Electrical characteristics of GaAs metal–oxide–semiconductor field effect transistor with atomic layer deposition deposited Al₂O₃ gate dielectric have been investigated. The IV characteristics were studied after various constant voltage stress (CVS) has been applied. A power law dependence of the gate leakage current (I_g) on the gate voltage (V_g) was found to fit the CVS data of the low positive V_g range. The percolation model well explains the degradation of I_g after a high positive V_g stress. A positive threshold voltage (V_th) shift for both +1.5 V and +2 V CVS was observed. Our data indicated that positive mobile charges may be first removed from the Al₂O₃ layer during the initial CVS, while the trapping of electrons by existing traps in the Al₂O₃ layer is responsible for the V_th shift during the subsequent CVS.     

用于GaAs射频集成电路的不同厚度氧化铝MIM 电容的研究

本文研究了不同厚度的氧化铝对MIM电容直流和射频特性的影响。在1MHz下,对于20nm氧化铝MIM电容,其拥有3850 pF/mm₂的高电容密度和可接受的681 ppm/V₂的VCC-α电压系数。1MHz时突出的74 ppm/V₂VCC-α电压系数,8.2GHz谐振频率以及2GHz时41的Q值可以从100nm氧化铝MIM电容获得。采用GaAs工艺以及原子层淀积制造的高性能ALD氧化铝MIM电容很有可能成为GaAs射频集成电路很有前景的候选器件。     

Ti~(3+):Al_2O_3激光特性的研究

本文详细报道了Ti~(3+):Al_2O_3激光器的实验结果.用一台Q开关脉冲Nd~(3+):YAG激光器的倍频光作泵浦源,获得了677～987nm调谐范围内O.5MW的峰值输出功率和13.9%的能量转换效率的TEM_(00)模输出.对实验结果进行了分析.l     

A 6.5-J flashlamp-pumped Ti:Al2O3 laser

A flashlamp-pumped Ti:A₂O₃ oscillator has delivered 6.5 J per pulse at 800 nm under long-pulse extraction conditions. The device was designed for efficient short-pulse (2-3 ns) amplification to the multijoule energy level. To date, a peak stored energy in excess of 5 J has been obtained and is available for short-pulse extraction studies. The design and resulting characterization of this laser are discussed. The results show that the energy available for short-pulse extraction is limited by the flashlamp pumping time