NH Film Research Articles

Origin of high‐density hole doping and anisotropic hole transport in a wide gap layered semiconductor LaCuOSe studied by first‐principles calculations

AbstractLaCuOSe is a wide gap (Eg = 2.8 eV) p‐type semiconductor. Epitaxial films may be converted to a degenerate semiconductor with hole concentrations (nh) > 1 × 1021 cm−3 by doping Mg ions to the La sites. We, however, found that the Mg concentration in the highest nh film was too low (<1%) to explain the high nh. Further, we observed large subgap absorption and no Burstein–Moss (BM) shift in the doped LaCuOSe, which contradict with a rigid‐band scheme. The doping stability was examined by density functional theory (DFT) calculations. The results showed that the substitution of the La site with an Mg ion needs a large extra energy and is not stable. Alternatively, copper vacancies are easily formed and work as shallow acceptors. On the other hand, it is also revealed that the calculation results are unable to explain the subgap absorption and the absence of a BM shift. Carrier transport calculations based on DFT and the Boltzmann transport theory were also performed, which provided information about anisotropic carrier transport in the layered crystal structure.

Viewing‐angle compensation of TN‐ and ECB‐LCD modes by using a rod‐like liquid‐crystalline polymer film

Abstract— A liquid‐crystal line retardation‐film technology by using a rod‐like liquid‐crystalline polymer (LCP) for various LCD modes have been developed. In particular, considerable improvements in viewing‐angle performance have been achieved for the twisted‐nematic (TN) and the transmissive/transflective electrically controlled birefringence (ECB) modes by using hybrid aligned nematic film (NH Film).

51.1: Invited Paper: Viewing‐Angle Compensation of TN‐ and ECB‐LCD Modes by Using a Rod‐Like Liquid Crystalline Polymer Film

AbstractWe have developed a liquid crystalline retardation film technology by using a rod‐like liquid crystalline polymer (LCP) for various LCD modes. In particular, considerable improvements in viewing angle performance have been achieved for the Twisted Nematic (TN) and the transmissive/transflective Electrically Controlled Birefringence (ECB) modes by using hybrid aligned nematic film ‘NH Film’.

P-137: Comparison of Viewing Angle Performance of TN-LCD and ECB-LCD Using Hybrid-Aligned Nematic Compensators

We compared the viewing angle performance of transmissive TN-LCD and ECB-LCD compensated with hybrid-aligned nematic films (NH film). We found that the ECB-LCD with NH film exhibited a wider high contrast ratio area and better grayscale performance than the TN-LCD with NH film. The ECB-LCD compensated with NH film is one of the most promising solutions for transmissive TFT-LCDs with a wide viewing angle performance.

P-116: Wide-Viewing-Angle Transflective LCD using Hybrid Aligned Nematic Compensators

A hybrid aligned nematic film (NH film) was developed as a viewing angle compensator for a transflective ECB-mode LCD with low driving voltage. By optimizing the parameters of the driving cell and NH films, the newly developed LCD compensated with two NH films exhibits extremely wide viewing-angle performance. This wide-viewing-angle system can be applied not only to transflective TFT-LCDs but also ordinary transmissive TFT-LCDs.

P‐106: Expansion of the High Iso‐Contrast Ratio Area for Transflective TFT‐LCDs with Hybrid Aligned Nematic Compensators

AbstractWe have developed a novel transflective TFT‐LCD with two hybrid aligned nematic compensators (NH film). Already we have presented the wide‐viewing angle transflective TFT‐LCD with one hybrid aligned nematic compensators. Based on the results of computer simulation, we introduced the second NH film, which located on the front of the LC cell, instead of the uniaxial film. We optimized the parameters of NH films, the retardation and the average tilted angle, by computer simulation. As the result, the newly developed TFT‐LCD with two NH films (retardation Δnd = 100nm, average tilt angle = 20degree) is viewable at wider angles than that with one NH film in transmissive mode. Viewing angle range (CR >10) of this LCD, reached 145 degree (vertical direction) and over 160 degree (horizontal direction). This wide‐viewing angle system can apply to not only transflective TFT‐LCD, but also ordinary transmissive one.

P‐122: Novel Ultra‐Thin Hybrid Aligned Nematic Compensators for Wide‐Viewing‐Angle Transflective TFT‐LCDs

AbstractWe have developed a novel ultra‐thin hybrid aligned nematic compensator (NH film) for wide‐viewing‐angle transflective TFT‐LCDs. The influence of the substrate film on the viewing angle performance is discussed. By eliminating the substrate of the NH film, the total thickness of the compensator can be reduced dramatically. We also confirmed the durability of this ultra‐thin compensator.

20.2: Wide‐Viewing‐Angle Transflective TFT‐LCDs with Hybrid Aligned Nematic Compensators

AbstractWe have developed a novel transflective TFT‐LCD with a hybrid aligned nematic compensator (NH film). We discuss the effects of the optical parameters of NH film based on the results of computer simulations. When the parameters are optimized, a newly developed display made with NH film exhibits a high contrast ratio and good grayscale stability over a wide range of viewing angles in the transmissive mode. In particular, grayscale inversion in the vertical direction is well restrained.

Properties of photochemically modified diamond films

Abstract Photochemical surface modification of polycrystalline diamond films was achieved. Clean, hydrogen-terminated diamond films were chlorinated by UV irradiation in Cl 2 (g). Amine-terminated diamond films were produced by irradiating the chlorinated diamond films in NH 3 (g). The modified surfaces were characterized by X-ray photoelectron spectroscopy and diffuse-reflectance Fourier transform infrared spectroscopy. The results of current-voltage ( I-V ) measurements indicated that surface modification by chlorine affected the ohmic nature of the gold-diamond contact, the contact resistance and the diamond surface conductivity.

A Study of Electrical, Metallurgical, and Mechanical Behaviors of Rapid Thermal Processed Ti Films in NH 3

The electrical, metallurgical, and mechanical behavior of the Ti films heat‐treated in a rapid thermal processor in and ambient in the temperature range of 550 to 750°C were studied. In addition, formation of the film by rapid thermal nitridation (RTN) in ambient and its barrier integrity were also studied as a function of the nitridation temperature and duration. n+ and p+‐type silicon and thermal oxide were used as substrates. Electron spectroscopy for chemical analysis, Rutherford backscattering spectroscopy, and sputtered neutral mass spectrometry were used to study the extent of the interactions between N, Ti, and Si as well as identification of the phase and its thickness. The thermal stability of the film as a diffusion barrier was investigated in the temperature range of 400 to 475°C. The diffusion barrier integrity of the film and its thermal stability were investigated via substrate junction leakage current and contact resistance measurements done on test structures fabricated using a complete 1.0 and 0.85 μm complimentary metal oxide semiconductor erasible programmable read‐only memory mask sets. Presented data shows that the decrease in the sheet resistance and the increase in the stress of the heat‐treated Ti films as the temperature increases are due to the presence of silicon in the Ti films. Similar results were obtained when heat‐treatment was carried out in ambient. The analytical analyses indicate that the thickest film which can be formed by the RTN process in ambient, in the temperature range of 590 to 750°C, is only 200 to 240 Å and is formed at about 600 to 610°C. The substrate junction leakage current data taken from the test structures indicate that the film formed by one‐step nitridation in ambient is not electrically and thermally reliable as a diffusion barrier for fabrication of the integrated circuit devices with shallow junctions (≤0.2 μm) regardless of the nitridation temperature and duration, and as‐deposited thickness of the Ti film. This short‐coming is attributed to an inadequate thickness of the film and the formation of (Ti‐Si‐Al) ternary solution. Finally, to overcome this problem, a multistep nitridation process was developed that produced the thickest film at the contacts and on the oxide layer (borophosphosilicate glass/borophosphosilicate tetraethyl orthosilicate), as well as a layer under the film at the contacts. The diffusion integrity of this bilayer was also evaluated via substrate junction leakage current and contact resistance measurements. The results indicate the suitability of this film as a diffusion barrier for submicron integrated circuit devices having shallow junctions. Furthermore, these results indicate that the presence of the layer under the layer at the contacts is essential if the film formed by RTN process in ambient is to be used as a diffusion barrier.

Latent image fading in mobile mammographic screening

I should like to comment in support of the letter by Robson et al (1992) and to provide further data on this topic, which is one of some concern to Breast Screening Programmes in remote areas. The film–screen system used in the Edinburgh Breast Screening Centre at the start of the national screening programme was Fuji NH film with Fuji Hi-Mammo screens and cassettes. This system was tested for latent image fading in July 1989, when 24 radiographs of a “Baits” phantom (White & Tucker, 1980) were obtained in under 1 h. The X-ray exposures were made on a Siemens Mammomat 2S unit in a screening van. This X-ray unit was chosen in preference to the units then available at the Centre because of the high reproducibility of its X-ray output. Of these 24 films, six were processed about 1 h after exposure (the shortest practicable time), six after a further 24 h, six at 1 week after exposure and the last six at 3 weeks after exposure. The mean background density of each set of six films is given in Table I, after correction for small changes in sensitometry speed index of the processor.

Oxidation of silicon (oxy)nitride and nitridation of silicon dioxide: Manifestations of the same chemical reaction system?

The study of the oxidation mechanism of low pressure and plasma-enhanced chemically vapour-deposited silicon nitride and oxynitride thin films in H 2OO 2 mixtures and the nitridation of SiO 2 thin films in NH 3 is motivated by the growing interest in these processes for use in microelectronics technology. In this paper, recent experimental results of oxidation and nitridation studies will be reviewed. Most reported data have been obtained using high energy ion beam analysis techniques. The results of (among others) hydrogen depth-profiling measurements unravel the essential role of hydrogen in the conversion of (oxy)nitride into oxide and of oxide into oxynitride. A unified picture describing the mechanisms of the oxidation and nitridation will be discussed.

Films, screens and cassettes for mammography

Various film-screen combinations intended for mammography have been compared for image quality and for dose. Image quality was assessed as in an earlier paper, using a test object having details which are both realistic and quantitative. Relative doses required to give film densities of 1.0 were measured. The Kodak MinR-MinR combination was taken as a standard against which others were compared, and in general a lower dose was accompanied by poorer image quality. The Fuji NH film with Fuji Hi-Mammo screen was the sole exception, giving slightly better image quality at about half the dose required by the MinR combination. A number of cassettes were also compared with each other and with evacuated envelopes. The Dupont Cronex cassette and three carbon-fibre fronted cassettes all performed well in image quality.