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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.

Fusarium wilt on strawberry plants caused by Fusarium oxysporum f. sp. fragariae (Fof) is a major disease in Korea. The prevalence of this disease is increasing, especially in hydroponic cultivation in strawberry field. This study assessed the effect of nutrition solution pH and electrical conductivity (EC) on Fusarium wilt in vitro and in field trials. pH levels of 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5 were assayed in vitro and in field trials. EC levels at 0, 0.5, 0.8, 1.0, and 1.5 dS∙m⁻¹ were assayed in field trials. Mycelial growth of Fof increased with increasing pH and was highest at 25°C pH 7 and lowest at 20°C, pH 5.0 in vitro. The incidence of Fusarium wilt was lowest in the pH 6.5 treatment and highest in the pH 5 treatment in field trials. At higher pH levels, the EC decreased in the drain solution and the potassium content of strawberry leaves increased. In the EC assay, the severity of Fusarium wilt and nitrogen content of leaves increased as the EC increased. These results indicate that Fusarium wilt is related to pH and EC in hydroponic culture of strawberry plants.

We aimed to fabricate reliable memory devices using HfO2, which is gaining attention as a charge-trapping layer material for next-generation NAND flash memory. To this end, a new atomic layer deposition process using sequential remote plasma (RP) and direct plasma (DP) was designed to create charge-trapping memory devices. Subsequently, the operational characteristics of the devices were analyzed based on the thickness ratio of thin films deposited using the sequential RP and DP processes. As the thickness of the initially RP-deposited thin film increased, the memory window and retention also increased, while the interface defect density and leakage current decreased. When the thickness of the RP-deposited thin film was 7 nm, a maximum memory window of 10.1 V was achieved at an operating voltage of ±10 V, and the interface trap density (Dit) reached a minimum value of 1.0 × 1012 eV−1cm−2. Once the RP-deposited thin film reaches a certain thickness, the ion bombardment effect from DP on the substrate is expected to decrease, improving the Si/SiO2/HfO2 interface and thereby enhancing device endurance and reliability. This study confirmed that the proposed sequential RP and DP deposition processes could resolve issues related to unstable interface layers, improve device performance, and enhance process throughput.

Developed over approximately half a century, neural probe technology is now a mature technology in terms of its fabrication technology and serves as a practical alternative to the traditional microwires for extracellular recording. Through extensive exploration of fabrication methods, structural shapes, materials, and stimulation functionalities, neural probes are now denser, more functional and reliable. Thus, applications of neural probes are not limited to extracellular recording, brain-machine interface, and deep brain stimulation, but also include a wide range of new applications such as brain mapping, restoration of neuronal functions, and investigation of brain disorders. However, the biggest limitation of the current neural probe technology is chronic reliability; neural probes that record with high fidelity in acute settings often fail to function reliably in chronic settings. While chronic viability is imperative for both clinical uses and animal experiments, achieving one is a major technological challenge due to the chronic foreign body response to the implant. Thus, this review aims to outline the factors that potentially affect chronic recording in chronological order of implantation, summarize the methods proposed to minimize each factor, and provide a performance comparison of the neural probes developed for chronic applications.

Peptide fragmentation and activity mapping of human lysozyme was carried out in order to define the structural and sequence requirements for anti-HIV activity. The findings suggest that the effects of HL9 on signaling pathways involved in survival, stress, TGF(beta), p53, NF(kappa)B, protein kinase C and hedgehog signaling may reflect changes in host cells that affect susceptibility to infection.

This study aims to investigate the influence of the sputtering pressure (PS) on Nb:TiO2-x films to enhance the bolometric properties. A decrease in the growth rate with the sputtering pressure was perceived in amorphous Nb:TiO2-x films. The incorporation of oxygen with PS was confirmed in an X-ray photo electron spectroscopy analysis. The electrical resistivity was increased with an increase in PS due to a decrease in the number of oxygen vacancies. The linear I-V characteristics confirmed the ohmic contact behavior between the Nb:TiO2-x layer and the electrode material. The present investigation finds that the sample with lower resistivity has good bolometric properties with low noise and high universal bolometric parameters. Finally, the Nb:TiO2-x sample deposited at a sputtering pressure of 2 mTorr shows better bolometric properties than other materials for infrared image sensor applications. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of the sputtering pressure (PS) on Nb:TiO2-x films to enhance the bolometric properties. A decrease in the growth rate with the sputtering pressure was perceived in amorphous Nb:TiO2-x films. The incorporation of oxygen with PS was confirmed in an X-ray photo electron spectroscopy analysis. The electrical resistivity was increased with an increase in PS due to a decrease in the number of oxygen vacancies. The linear I-V characteristics confirmed the ohmic contact behavior between the Nb:TiO2-x layer and the electrode material. The present investigation finds that the sample with lower resistivity has good bolometric properties with low noise and high universal bolometric parameters. Finally, the Nb:TiO2-x sample deposited at a sputtering pressure of 2 mTorr shows better bolometric properties than other materials for infrared image sensor applications. [ABSTRACT FROM AUTHOR]

Understanding the relationship between a certain organic material and the corresponding orthogonal solvent improves the realistic possibility of photolithographic patterning during the fabrication of organic devices. However, an all-solution-based patterning process has not been established because the dry-etching process used for micropatterning must be performed in a vacuum chamber, which is not appropriate for a printing process and results in a low throughput of products at the industrial level. Here, we demonstrate a vacuum-free patterning method using conventional photolithography. It is a main breakthrough in that it washes away the etchant by blowing with air in a very short time. This short-term air-blowing process dramatically reduces the undercut below the photoresist. As a result, mask patterns of nearly the same size could be transferred onto an organic object. Compared with ordinary wet etching process, the undercut is reduced to the 1-micrometer scale, allowing the realisation of a fine pattern size. The process developed here will enhance the throughput of manufacturing systems using an all-solution-based process. [ABSTRACT FROM AUTHOR]

A nanoporous Pirani sensor based on anodic aluminum oxide (AAO) is proposed, and the quantitative relationship between the performance of the sensor and the porosity of the AAO membrane is characterized with a theoretical model. The proposed Pirani sensor is composed of a metallic resistor on a suspended nanoporous membrane, which simultaneously serves as the sensing area and the supporting structure. The AAO membrane has numerous vertically-tufted nanopores, resulting in a lower measurable pressure limit due to both the increased effective sensing area and the decreased effective thermal loss through the supporting structure. Additionally, the suspended AAO membrane structure, with its outer periphery anchored to the substrate, known as a closed-type design, is demonstrated using nanopores of AAO as an etch hole without a bulk micromachining process used on the substrate. In a CMOS-compatible process, a 200 µm 200 µm nanoporous Pirani sensor with porosity of 25% was capable of measuring the pressure from 0.1 mTorr to 760 Torr. With adjustment of the porosity of the AAO, the measurable range could be extended toward lower pressures of more than one decade compared to a nonporous membrane with an identical footprint. [ABSTRACT FROM AUTHOR]

A ferroelectric-gated graphene field-effect transistor was fabricated by consecutively stacking two distinct graphene-ferroelectric hybrid ribbons at right angles. Two graphene layers play different roles. One graphene layer acts as a gate electrode and the other graphene layer acts as a channel between two electrodes, source and drain. Electric gating at the gate graphene modulates the resistance of the channel graphene. By means of ferroelectric polarisation, bistable resistance states of the channel graphene could be recorded, and the retention time of bistability was estimated to be 460 days by extrapolating of two resistance values in time-resistance relationships. Furthermore, the underlying concept to fabricate bistable memory device was extended to the methodology to realise a logic-gate device by stacking three distinct graphene-ferroelectric hybrid ribbons. [ABSTRACT FROM AUTHOR]

The effect of thermal annealing on the bolometric properties of TiO2-x films was investigated. The test-patterned TiO2-x samples were annealed at 300°C temperature in order to enhance their structural and electrical properties for effective infrared image sensor device applications. The crystallinity was changed from amorphous to rutile/anatase in annealed TiO2-x films. Compared to the as-deposited samples, a decrement of the band gap and a decrease of the electrical resistivity were perceived in annealed samples. We found that the annealed samples show linear current-voltage (I-V) characteristic performance, which implies that ohmic contact was well formed at the interface between the TiO2-x and the Ti electrode. Moreover, the annealed TiO2-x sample had a significantly low 1/f noise parameter (1.21×10-13) with a high bolometric parameter (β) value compared to those of the asdeposited samples. As a result, the thermal annealing process can be used to prepare TiO2-x film for a high-performance bolometric device. [ABSTRACT FROM AUTHOR]

Purpose: Active reduced dose tetanus-diphtheria-acellular pertussis (Tdap) vaccination for adolescents and adults is necessary because waning immunity after primary diphtheria- tetanus-pertussis vaccination is related to the recent emergence of pertussis. This study was conducted to compare the immunogenicity and protection efficacy against Bordetella pertussis between a new GCC Tdap vaccine and a commercially available Tdap vaccine in a murine model. Materials and Methods: BALB/c mice were immunized with two doses of diphtheria-tetanusacellular pertussis (DTaP) vaccine for priming and a subsequent Tdap booster vaccination. According to the type of booster vaccine, mice were divided into four groups: commercially available Tdap vaccine in group 1 and GCC Tdap vaccines of different combinations of pertussis antigens in groups 2 to 4. Humoral and cell-mediated immune responses and protection efficacy using a murine intranasal challenge model after booster vaccination were compared among the four groups. Results: Every group showed significant increases in antibody titers against pertussis antigens such as pertussis toxin, filamentous hemagglutinin, and pertactin after booster vaccination. Spleen cells showed both Th1 and Th2 cell-mediated immune responses stimulated by pertussis antigens in all groups without any significant difference. In the intranasal B. pertussis infection model, bacteria were eradicated in all groups five days after challenge infection. Conclusion: This preliminary study did not show significantly different immunogenicity or protection efficacy of the new GCC Tdap vaccines compared to the commercially available Tdap vaccine, although a more extensive study is necessary to assess the differing efficacies of the new GCC Tdap vaccines. [ABSTRACT FROM AUTHOR]

This paper describes a new CMOS readout circuit, which makes the microbolometer focal plane array have low spatial noise over a wide operating temperature range without a thermoelectric cooler. The readout circuit corrects the nonuniformity of each microbolometer pixel by the proposed self-bias equalization technique. The proposed readout circuit adopting the self-bias equalization has a feedback loop that makes the readout circuit find the bias voltage for the correction of nonuniformity by itself. The proposed circuit was fabricated using a 0.35-μm standard CMOS process. The measured results of the fabricated chip show that the spatial noise is less than the allowed spatial noise for the equivalent temperature difference of 50 mK over a wide operating temperature range. [ABSTRACT FROM PUBLISHER]

An analytical model for the electro-thermal feedback effect in a microbolometer infrared focal plane array is presented. The presented model is the integrated optical-electro-thermal model, in which the electrothermal feedback effect incorporated with the response of incident IR can be described. In addition, since the model is based on physics, the model parameters also have their own physical meaning. This analytical model can be easily utilized to describe the temperature increase caused by the applied heat sources and has a unique feature describing capability of optical-electro-thermal analysis in a quasi-steady-state, which can hardly be performed with thermal analysis tools based on the finite element method. The model shows that the temperature of the microbolometer in this study can be increased 7.1% to 18.6% more by the electro-thermal feedback effect. [ABSTRACT FROM AUTHOR]

In order to acquire radiation-tolerant characteristics in integrated circuits, a dummy gate-assisted n-type metal oxide semiconductor field effect transistor (DGA n-MOSFET) layout was adopted. The DGA n-MOSFET has a different channel shape compared with the standard n-MOSFET. The standard n-MOSFET has a rectangular channel shape, whereas the DGA n-MOSFET has an extended rectangular shape at the edge of the source and drain, which affects its aspect ratio. In order to increase its practical use, a new aspect ratio model is proposed for the DGA n-MOSFET and this model is evaluated through three-dimensional simulations and measurements of the fabricated devices. The proposed aspect ratio model for the DGA n-MOSFET exhibits good agreement with the simulation and measurement results. [ABSTRACT FROM AUTHOR]

To identify the primary factor affected the decreased PM10 concentration in Seoul which is the capital city of Korea, wind speed and emissions in 2003 and 2004 were analyzed. The level of air pollution is intense in Seoul and continually increased since the late 1990s. However the concentration of PM10 has been greatly declined recently. In particular, the concentration of PM10 decreased 14% in 2003 and 2004 excluding the Asian dust periods. It is suggested that the major factors for the decrease are differences in wind speed between the two years and the period of constant breeze. In 2003, intense Asian dust events happened frequently and it increased the concentration of total PM10. The intense dust events were influence by the speed and duration of the wind. It is considered that the meteorological condition was the primary drive for the change of the concentration of PM10. The decreased emissions seem to be the additional factor for the change in the concentration of PM10. [ABSTRACT FROM AUTHOR]

Although ferroelectric materials are attractive due to their non-volatility originating from their spontaneous polarisation, advances in integrated density of these materials are required. To overcome the poor integration density compared with silicon integrated circuits, the concept of multi-bit memory has arisen. Previous ferroelectric multi-bit memory devices were developed through the realisation of a framework of two laterally neighbouring capacitors, in which both capacitors have different thicknesses for individual switching in different voltage ranges. However, a reliability issue with regard to limiting the additional scale down of these materials to the sub-100 nm level arose due to self-crosstalk, which was defined as a protrusion of the electric fringing field when a logic state was written in a multi-bit memory device. Here, self-crosstalk by simulating an electric field distribution in a multi-bit memory cell based on an actual sample fabricated with a ferroelectric polymer, after which they suggest a new three-dimensional structure of the ferroelectric multi-bit memory device to eliminate self-crosstalk. [ABSTRACT FROM AUTHOR]

In this article, silicon bulk micromachined RF MEMS switch with four cantilever piezoelectric actuators has been designed, fabricated, and characterized for advanced mobile/wireless communication systems. The proposed switch is comprised of four piezoelectric cantilever actuators, a contact metal pad, and a suspended CPW signal line above the silicon substrate. The fabricated piezoelectric switch has an insertion loss of -0.23 dB and an isolation of -44 dB at a frequency of 2 GHz and an operation voltage of 2.5 V, respectively. Also, it has constant performance characteristics at the certain range of applied voltages above the operation voltage that result in high production yield. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 570–573, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22195 [ABSTRACT FROM AUTHOR]

In this paper, fully integrated film bulk acoustic resonators (FBARs) and filter have been designed, fabricated, and characterized by using silicon bulk micromachining technology. The fabricated resonator is comprised of aluminum nitride (AlN) piezoelectric material sandwiched by two molybdenum (Mo) electrodes on top of silicon nitride thin membrane. The developed AlN piezoelectric film has 1.9° of FWHM (full width half maximum) of rocking curve and approximately 70 Mpa in tensile stress on top of the Mo electrode. The fabricated FBAR has a quality factor of 1530 in size of 200 × 200 μm2, insertion loss of -0.45 dB, and return loss of -28 dB, respectively. The fabricated FBAR ladder type filter is comprised of 7 resonators with 3 resonators in series and 4 resonators in parallel. It has insertion loss of -3.2 dB and ripple of 0.4 dB in pass band, absolute attenuation of 40 and 50 dB at 1.6–1.875 GHz and 2.110–2.170 GHz, respectively. The size of the fabricated FBAR filter is 1.2 mm × 1.4 mm before packaging and 3 mm × 3 mm after packaging, respectively. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2230–2233, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21905 [ABSTRACT FROM AUTHOR]

A new readout circuit involving two-step current-mode background suppression is studied for two-dimensional long-wavelength infrared focal plane arrays (2-D LWIR FPAs). Buffered direct injection (BDI) and a feedback amplifier are used for the input circuit and background suppression circuit, respectively. The readout circuit has been fabricated using a 0.6-μm 2-poly 3-metal CMOS process for a 64 × 64 LWIR HgCdTe IR array with a pixel size of 50 μm e× 50 μm. The simple pixel circuit has a very small skimming error of less than 0.3% and low noise characteristics for an adequate calibration range and integration time. [ABSTRACT FROM AUTHOR]

A multiple integration method is reported that greatly improves the signal-to-noise ratio (SNR) for applications with a high-resolution infrared (IR) focal plane array. The signal from each pixel is repeatedly sampled into an integration capacitor and then output and summed into an outside memory that continues for n read cycles during each period of a frame. This method increases the effective capacity of the charge integration and improves sensitivity. Because a low-noise function block and high-speed operation of the readout circuit is required, a new concept is proposed that enables the readout circuit to perform digitization by a voltage skimming method. The readout circuit was fabricated using a 0.6-μm CMOS process for a 64 × 64 midwavelength IR HgCdTe detector array. The readout circuit effectively increases the charge storage capacity to 2.4 × 108 electrons and then provides a greatly improved SNR by a factor of approximately 3. [ABSTRACT FROM AUTHOR]

The yeast heme activator protein Hap1 binds to DNA and activates transcription of genes encoding functions required for respiration and for controlling oxidative damage, in response to heme. Hap1 contains a DNA-binding domain with a C6 zinc cluster motif, a coiled-coil dimerization element, typical of the members of the yeast Gal4 family, and an acidic activation domain. Tile regulation of Hap1 transcription-activating activity is controlled by two classes of Hap1 elements, repression modules (RPM1–3) and heme-responsive motifs (HRM1-7). Previous indirect evidence indicates that Hap1 may repress transcription directly. Here we show, by promoter analysis, by chromatin immunoprecipitation, and by electrophoretic mobility shift assay, that Hap1 binds directly to DNA and represses transcription of its own gene by at least 20-fold. We found that Hap1 repression of the HAP1 gene occurs independently of heme concentrations. While DNA binding is required for transcriptional repression by Hap1, deletion of Hap1 activation domain and heme-regulatory elements has varying effects on repression. Further, we found that repression by Hap1 requires the function of Hsp70 (Ssa), but not Hsp90. These results show that Hap1 binds to its own promoter and represses transcription in a heme-independent but Hsp70-dependent manner. [ABSTRACT FROM AUTHOR]

The pseudodielectric-function spectra, ε(E) = ε1(E) + iε2(E), of polycrystalline Cd0.9Zn0.1Te thin films in the 1.7–5.5 eV photon energy range were measured by spectroscopic ellipsometry. The measured dielectric function spectra reveal distinct structures at energies of the E1, E1 + Δ1 and E2 critical points due to interband transitions. The vacuum evaporated Cd0.9Zn0.1Te thin films exhibited zinc-blende structure with predominant (111) orientation. The rms roughness of the film evaluated by an ex-situ atomic force microscopy is 3.7 nm. Dielectric related optical constants, determined from the spectroscopic ellipsometry data are presented and analyzed. The optical constants of the film were also determined by using optical transmittance measurements, and results were discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Heme-responsive motifs (HRMs) mediate heme regulation of diverse regulatory proteins. The heme activator protein Hap1 contains seven HRMs, but only one of them, HRM7, is essential for heme activation of Hap1. To better understand the molecular basis underlying the biological significance of HRMs, we examined the effects of various mutations of HRM7 on Hap1. We found that diverse mutations of HRM7 significantly diminished the extent of Hap1 activation by heme and moderately enhanced the interaction of Hap1 with Hsp90. Furthermore, deletions of nonregulatory sequences completely abolished heme activation of Hap1 and greatly enhanced the interaction of Hap1 with Hsp90. These results show that the biological functions of HRMs and Hsp90 are highly sensitive to structural changes. The unique role of HRM7 in heme activation stems from its specific structural environment, not its mere presence. Likewise, the role of Hsp90 in Hap1 activation is dictated by the conformational or structural state of Hap1, not by the mere strength of Hap1-Hsp90 interaction. It appears likely that HRM7 and Hsp90 act together to promote the Hap1 conformational changes that are necessary for Hap1 activation. Such fundamental mechanisms of HRM-Hsp90 cooperation may operate in diverse regulatory systems to mediate signal transduction. [ABSTRACT FROM AUTHOR]

Coercive voltages (VC, the voltage which makes remanent polarization zero in ferroelectrics) of metal-ferroelectric polymer-metal capacitors were measured with different pulse periods. From the measured VC, coercive fields (EC, normalized VC for thickness) and internal bias fields (EBIAS) were calculated. Although EC was found to be nearly constant with thickness, EBIAS increased as thickness decreased. Based on these findings, it appears that EBIAS can be induced from interface phenomenon and greatly affects retention performance in thin ferroelectric films used for nonvolatile memory devices. [ABSTRACT FROM AUTHOR]

For nonvolatile memory devices, capacitors with metal-ferroelectric-metal structures were fabricated using poly(vinylidene fluoride-trifluoroethylene) as a ferroelectric layer, and performance was estimated in terms of retention property. In the same thickness, the polarization retained longer as the writing pulsewidth (PW) was extended. With the same writing PW, a thicker capacitor maintained a polarized state longer. In conclusion, the performance for operating voltage, operating frequency, and data retention time is expected. [ABSTRACT FROM AUTHOR]

A capacitive microcantilever-type infrared (IR) detector having a unique structure that has high immunity to thermomechanical noise (TM-noise) is proposed. The device has a capacitive readout scheme and is compared with a conventional design using the same readout method by finite element model simulation. The total cantilever length was halved, compared with the conventional device structure, in order to increase the device's spring constant, and the IR absorber area was consequently increased as the portion of the leg in the given pixel area is decreased. Large spring constant and increased absorber area are the main causes of the TM-noise reduction. The feasibility of the device was shown by fabrication, and measured parameters demonstrated the structure's superiority. It was shown that the proposed structure potentially has low TM-noise and an overall noise-equivalent temperature difference (NETD) value that is lower than that of the conventional designed device. The NETD of the proposed device was found to be 5.7 mK. [ABSTRACT FROM AUTHOR]

Calculated chemical equations using thermodynamics suggest that elemental Te0 is easily induced during bromine-based etching process on the HgCdTe surface and the induced elemental Te0 can be removed by chemical reaction with hydrazine, forming volatile H2Te. X-ray photoelectron spectroscopy (XPS) confirmed these chemical reactions. The induced elemental Te0 is believed to play a role as surface generation-recombination centers in CdTe/HgCdTe interface, which was confirmed by XPS, ideality factor, and energy-dispersive interface trap density (Dit) analyses. [ABSTRACT FROM AUTHOR]

In this letter, the effect of annealing in plasma-induced-type converted HgCdTe was observed. The Hg deficient annealing process reconverts the type converted n-HgCdTe into p-type. The activation energy of the process was determined to be 0.99eV regardless to the gas species used for the type conversion process. However, the absorption edge moved toward short-wave direction for hydrogen-plasma-treated sample. The absorption edge shift was observed even after the annealing process, which means the passivation and junction formation are separate phenomena. [ABSTRACT FROM AUTHOR]

In this paper, fully integrated radio frequency (RF) microelectromechanical system (MEMS) switches with piezoelectric actuation have been proposed, designed, fabricated, and characterized. At a very low operation voltage of 2.5V, reliable and reproducible operation of the fabricated switch was obtained. The proposed RF MEMS switch is comprised of a piezoelectric cantilever actuator with a floated contact electrode and isolated CPW transmission line suspended above the silicon substrate. The measured insertion loss and isolation of the fabricated piezoelectric switch are -0.22 dB and -42dB at a frequency of 2GHz, respectively. [ABSTRACT FROM PUBLISHER]

This work extends the kinds of organic materials that can form nano-lens arrays (NLAs). We have previously addressed fabrication of a N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) NLA and explained the formation mechanism as NPB crystallization and the resulting increase in surface tension. Here, we report a Tris(8-hydroxyquinolinato)aluminum (Alq3) NLA fabricated by the same deposition method as a NPB NLA. Grazing-incidence small-angle X-ray scattering experiments indicate that the formation mechanism of the Alq3 NLA is the same as that of the NPB NLA. Furthermore, this study broadens the application of NLAs from rigid to flexible organic light-emitting diodes (OLEDs). Here, flexible stainless steel-based devices using a low-temperature thermal release film, atomic layer deposition and NPB NLA processes are fabricated and characterized. With a NLA, current efficiency is increased 1.4 times, indicating that fab-compatible NLA technology is also available for flexible OLEDs. [ABSTRACT FROM AUTHOR]

In order to reduce the sun-burn effect in a sample of the bolometric material Nb:TiO2−x, oxygen annealing was carried out. This effect can be examined by comparing thermal stability test results between the as-deposited and oxygen-atmosphere-annealed samples under high-temperature exposure conditions. Structural studies confirm the presence of amorphous and rutile phases in the as-deposited and annealed samples, respectively. Composition studies reveal the offset of oxygen vacancies in the Nb:TiO2−x samples through oxygen-atmosphere annealing. The oxygen atoms were diffused and seemed to occupy the vacant sites in the annealed samples. As a result, the annealed samples show better thermal stability performance than the as-deposited samples. The universal bolometric parameter (β) values were slightly decreased in the oxygen-annealed Nb:TiO2−x samples. Although bolometric performance was slightly decreased in the oxygen-annealed samples, high thermal stability would be the most essential factor in the case of special applications, such as the military and space industries. Finally, these results will be very useful for reducing the sun-burn effect in infrared detectors. [ABSTRACT FROM AUTHOR]

A heat-sensitive layer (TiO2−x) was successfully deposited by RF reactive magnetron sputtering for infrared (IR) image sensors at different relative mass flow of oxygen gas (RO2) levels. The deposition rate was decreased with an increase in the percentage of RO2 from 3.4% to 3.7%. TiO2−x samples deposited at room temperature exhibited amorphous characteristics. Oxygen deficiency causes a change in the oxidation state and is assumed to decrease the Ti4+ component on the surfaces of TiO2−x films. The oxygen stoichiometry (x) in TiO2−x films decreased from 0.35 to 0.05 with increasing the RO2 level from 3.4% to 3.7%, respectively. In TiO2−x−test-patterned samples, the resistivity decreased with the temperature, confirming the typical semiconducting property. The bolometric properties of the resistivity, temperature coefficient of resistance (TCR), and the flicker (1/ f) noise parameter were determined at different x values in TiO2−x samples. The rate of TCR dependency with regard to the 1/ f noise parameter is a universal bolometric parameter (β), acting as the dynamic element in a bolometer. It is high when a sample has a relatively low resistivity (0.82 Ω·cm) and a lower 1/ f noise parameter (3.16   ×   10−12). The results of this study indicate that reactively sputtered TiO2−x is a viable bolometric material for uncooled IR image sensor devices. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of gamma radiation on ZnS/CdTe-passivated HgCdTe photodiodes that were fabricated with one of two different surface treatments using bromine, Br2, or hydrazine, N2H4. Unlike the ZnS-passivated HgCdTe photodiodes, the ZnS/CdTe-passivated HgCdTe photodiodes showed no degradation in resistance-area product at zero bias (R0A) values after gamma irradiation of up to 1 Mrad. However, there is a significant difference between the bromine- and hydrazine-treated samples. Regardless of the dose of gamma radiation, there was little change in the forward current characteristics of the hydrazine-treated diode in comparison with the conventional bromine-treated diode. The hydrazine-treated diode showed fairly uniform R0A values of > 107 Ω-cm² up to 1 Mrad of gamma irradiation, whereas the bromine-treated diode showed an abrupt change in R0A values from ∼106 Ω-cm² to ∼107 Ω-cm² after gamma irradiation. Therefore, for use in a gamma radiation environment, the best combination for high-performance HgCdTe photodiodes is a ZnS/CdTe passivant that has been treated with hydrazine. [ABSTRACT FROM AUTHOR]

To develop plasma-resistant glass materials suitable for semiconductor etching processes, we introduced alkaline earth oxides (ROs) into a Li2O–Al2O3–SiO2 (LAS) glass. Analysis of glass properties with respect to the additives revealed that among the analyzed materials, the LAS material in which Li2O was partially replaced by MgO (MLAS) exhibited the most favorable characteristics, including a low dielectric constant (6.3) and thermal expansion coefficient (2.302 × 10−6/°C). The high performance of MLAS is attributed to the high ionic field strength of Mg2+ ions, which restricts the movement of Li+ ions under the influence of electric fields and thermal vibrations at elevated temperatures. When exposed to CF4/O2/Ar plasma, the etching speed of RO-doped glasses decreased compared with that of quartz and LAS glass, primarily owing to the generation of a high-sublimation-point fluoride layer on the surface. Herein, MLAS demonstrated the slowest etching speed, indicating exceptional plasma resistance. X-ray photoelectron spectroscopy analysis conducted immediately after plasma etching revealed that the oxidation-to-fluorination ratio of Li was the lowest for MLAS. This observation suggests that the presence of Mg2+ ions in the plasma discharge inhibits the migration of Li+ ions toward the surface, thereby contributing to the excellent plasma resistance of MLAS.

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.