Oblique Vapour Incidence Research Articles

Morphology of Thin Films Formed by Oblique Physical Vapor Deposition

Physical vapor deposition is a fundamental tool to create thin films for countless applications. Deposition at oblique vapor incidence angles can lead to the growth of thin films with dramatically changed morphological features. Techniques such as oblique angle deposition (OAD) and glancing angle deposition (GLAD) utilize this fact to create self-organized nanostructures on surfaces. The changed columnar microstructure of such thin films significantly influences the film properties. The film density, for instance, influences the refractive index and therefore has impact for optical applications, like filters or antireflection coatings. Understanding the influence of the incidence angle in physical vapor deposition is an important step that allows tailoring the nanostructured surfaces for specific applications not only in optics, but also for catalysis or biosensing usage. To investigate thin film growth at oblique deposition conditions, silicon, germanium, and molybdenum nanostructured thin films were dep...

Effect of Using Oblique-Incidence Deposited Ru Interlayers Deposited by Evaporation and Sputtering on Recording Characteristics of Perpendicular Media

Oblique-incidence evaporation and sputtering were performed to investigate the effect of reducing the Ru interlayer thickness on the recording characteristics of perpendicular magnetic recording media. Deep gaps were observed at grain boundaries on oblique-incidence evaporated and sputtered films when the incident angle was over 60 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . Evaporated Ru films have a lower density than sputtered Ru films at the same incident angle. This indicates that the self-shadowing effect predominantly occurs due to suppression of migration of deposited atoms for evaporation films. However, degradation of the crystal orientation is observed in evaporated Ru films due to the present experimental limitations. Examination of the recording characteristics revealed that the Ru interlayer thickness can be reduced by using an oblique-incidence sputtered Ru interlayer and the writing ability can be improved by reducing the spacing loss between the head and the soft magnetic underlayer.

Morphology and texture evolution of nanostructuredCaF2 films on amorphous substrates under oblique incidence flux

The morphology and biaxial texture of vacuum evaporatedCaF2 films on amorphous substrates as a function of vapour incident angle, substratetemperature and film thickness were investigated by scanning electron microscopy,x-ray pole figure and reflection high energy electron diffraction surface pole figureanalyses. Results show that an anomalous [220] out-of-plane texture was preferred inCaF2 films deposited onSi substrates at < 200 °C with normal vapour incidence. With an increase of the vapour incident angle, theout-of-plane orientation changed from [220] to [111] at a substrate temperature of100 °C. Infilms deposited with normal vapour incidence, the out-of-plane orientation changed from [220] at100 °C to [111]at 400 °C. In films deposited with an oblique vapour incidence at100 °C, the texture changed from random at small thickness (5 nm) to biaxial at larger thickness(20 nm or more). Using first principles density functional theory calculation, it was shownthat [220] texture formation is a consequence of energetically favourable adsorption ofCaF2 moleculesonto the CaF2(110) facet.

Study of magnetic anisotropy and magnetoresistance effects in ferromagnetic Co/Au multilayer films prepared by oblique incidence evaporation method

A series of e-beam evaporated [Co10 Å/Au t Å] 20 multilayers has been deposited on 1.69 mm 2 glass substrates. The samples were examined with vibrating sample magnetometer, low angle X-ray diffraction, and magnetoresistance (MR) measurements. The effects of oblique incidence evaporation and magnetic annealing on the anisotropy, microstructure, and different components of MR are examined. After magnetic annealing, the multilayer [Co10 Å/Au20 Å] 20 produced at the incidence angle of 45° showed a strong anisotropy and the easy axis of the anisotropy is along the perpendicular ( x-axis; along the film plane) to the incidence of evaporation. MR at room temperature has two components: isotropic and anisotropic. The magnetoresistance effects are found to be larger in the uniaxial films, with both anisotropic and giant magnetoresistance peaking at around 20 Å Au layer thickness.

Nanostructured gradient index optical filter for high-speed humidity sensing

A high-speed optical humidity sensor was fabricated from a nanostructured titanium dioxide thin film. A refractive index depth profile designed to yield a narrow-bandpass optical interference filter was obtained through nanoscale porosity variations produced by a physical vapor deposition technique known as glancing angle deposition (GLAD). The GLAD process provides film morphology control on the 10 nm scale through a combination of deposition at highly oblique vapor incidence angles and controlled substrate motion. Under varying humidity conditions the transmittance spectrum of the filter shifts due to effective index changes of the porous structure resulting from water vapor adsorption/desorption. Performance analysis has shown that this device is highly sensitive, exhibits minimal hysteresis, and is extremely fast. The adsorption and desorption response times were measured to be 270 ms and 160 ms, respectively.

Effects of oblique-incidence evaporation on magnetic properties of Fe 20Ni 80/Fe 70Co 30 bilayer film

Evaporative deposition at oblique incidence is shown to enhance the magnetic anisotropy of an Fe 20Ni 80 magnetic film and induce magnetic anisotropy in an overlying, strongly isotropic Fe 70Co 30 film. This deposition method for the formation of an underlayer of several lattice parameters in thickness and semi-hard overlayer of a few thousands Angstroms in thickness achieves a significant change in the magnetization process and strong suppression of the coercive forces of Fe 70Co 30 in the hard magnetization direction. Soft magnetization of the Fe 70Co 30 overlayer is not achieved when one of the layers is deposited at oblique incidence. It is anticipated that shape magnetic anisotropy is responsible in part for the magnetic anisotropy induced in both in Fe 20Ni 80 under- and Fe 70Co 30 overlayer by oblique incidence evaporation.

Soft magnetization of a semi-hard/soft magnetic bilayer produced by oblique-incidence evaporation

The possibility of achieving soft magnetization in semi-hard magnetic films such as Fe, Fe 93.5Si 6.5, Fe 50Co 50 and Fe 70Co 30 is investigated by depositing films on an Fe 20Ni 80 underlayer by oblique-incidence evaporation. The magnetic anisotropy of the underlayer is strengthened to a depth of several lattice parameters by vapor deposition of the film at an oblique angle to the substrate surface. This method also allows magnetic anisotropy to be induced in strongly isotropic semi-hard magnetic overlayers to a thickness of a few thousands Angstroms. The coercive force of bilayer films measured along the hard-axis is reduced remarkably by this process, and the strength of the anisotropy field is demonstrated to be readily controllable. When magnetic anisotropy exists in both magnetic layers, a significant change is observed in the magnetization processes of the semi-hard magnetic layer and the coercive forces in the hard magnetization direction is dramatically reduced. Soft magnetization of the semi-hard magnetic layer cannot be achieved when magnetic anisotropy exists in only one of the magnetic layers.

Effect of magnetic anisotropy on soft magnetization of Fe, Fe50Co50 and Fe70Co30 films

An FeNiMo underlayer with magnetic anisotropy is shown to readily induce magnetic anisotropy in an overlying FeCoV or Fe50Ni50 layer and suppress the coercive force of these overlayers by about 90–97%. The exact nature of the change in magnetic behavior of the overlayers and the degree of coercive force reduction are confirmed to be dependent on the existence and direction of magnetic anisotropy in those layers upon deposition. The soft magnetization of Fe, Fe50Co50 and Fe70Co30 films with isotropic magnetization processes deposited on an Fe20Ni80 underlayer with magnetic anisotropy is successfully achieved by introducing magnetic anisotropy into the semi-hard magnetic overlayers by oblique-incidence evaporation. The coercive forces of Fe20Ni80/Fe, Fe20Ni80/Fe50Co50 and Fe20Ni80/Fe70Co30 bilayer films are reduced remarkably by this process, and the strength of the anisotropic magnetic field is demonstrated to be readily controllable by this method.

Microstructure Modification of Yttria-Stabilized Zirconia Layers Prepared by EB-PVD

Microstructures and texture of yttria-stabilized zirconia (YSZ) layers prepared by electron beam physical vapor deposition (EB-PVD) were investigated, addressing the effect of processing parameters. All the YSZ layers investigated in this study showed a columnar structure. However, significant differences were found in their microstructures. Morphology, porosity, and texture of the layers changed drastically by substrate manipulation during deposition. Without rotation, the layer showed a dense columnar structure with less intercolumnar gaps and obscure feather-like structures, and no preferred growth orientation. Rotation was very effective in developing feather-like structures within each column and hence increasing porosity. In addition, substrate rotation caused strong (100) texture. These results are attributed to the flux shadowing effect induced by oblique vapor incidence caused by substrate manipulation. The influence of electron beam power and substrate temperature was also investigated.

Electrical resistivity and magnetism of Fe/Si multilayers prepared by oblique incidence evaporation

We discussed the origin of the uniaxial magnetic anisotropy of the Fe/Si multilayered films prepared by varying oblique evaporation angle from the view of electric resistance. The tendency in the incidence angle dependence of the uniaxial magnetic anisotropy is in agreement with that of the angle dependence of the electric resistance ratio. The origin of the magnetic anisotropy seems to be due to anisotropic arrangement of atoms in the film.

The effect of oblique incidence evaporation on the magnetic properties of thin film elements

The magnetic properties of micrometre-sized thin film elements fabricated by electron beam lithography have been investigated for films evaporated under different conditions. Using the well established technique of varying the angle of incidence of evaporation we have produced elements with an additional contribution to the anisotropy. Lorentz microscopy has been used to study the effect of this anisotropy on the domain structures and switching behaviour for acicular elements which already possess a strong shape anisotropy. Our observations for elements with the induced anisotropy either parallel or perpendicular to the shape anisotropy indicate that the demagnetizing effects are still dominant. However the hysteresis loops and magnetization reversal of the elements are changed considerably with the additional constraint of induced anisotropy.

A high-performance, flexible substrate for thin-film media

Advances in magnetic recording tape and flexible disk systems are limited to a large extent by the properties of the substrate, particularly for the case of evaporated or sputtered thin-film media. In this paper we report on the magnetic properties of thin-film media deposited onto a new high-performance polymeric film with improved tensile strength, which can withstand temperatures as high as 600°C without any adverse effects. Good magnetic properties were obtained by oblique incidence evaporation of cobalt films onto the heated substrates.

An X-ray fourier line shape analysis of hexagonal tellurium films III: Vacuum evaporated onto air-cleaved mica substrates at low temperature (133 K)

As a continuation of a series of studies of hexagonal tellurium films deposited onto glass at room temperature and low temperature (133 K), investigations were carried out on the growth structure of tellurium films 331–800 nm thick (for normal vapour incidence) and 260–1129 nm thick (for oblique vapour incidence) deposited by vacuum evaporation at various rates of deposition onto air-cleaved mica substrates at a temperature of 133 K. Since mica is a crystalline substrate it was used to study its influence on the growth structures and preferred orientation. Considering the cases of normal and oblique vapour incidence for both high and low rates of deposition, a small domain or crystalline size effect (about 115–160 Å), appreciable microstrains (2.2–5.0)×10 -3 in the domains and a near-isotropy in the size and strain parameters were observed from a detailed Fourier analysis of X-ray diffraction profiles. The results obtained from the analysis of fault-affected reflections ( H - K = 3 N±1, L 0 odd or even) show that the intrinsic stacking faults (probability α) are totally absent and the presence of growth stacking faults (probability β) is also negligible. The dislocation density ϱ is about 10 11 cm -2 and a c axis texture is found to develop in the films. The average residual internal stresses σ and lattice parameter changes Δ a and Δ c, obtained from line shift analysis, are small. From a comparison of the results obtained for the different cases it appears that the changes in the angle of deposition or the rate of deposition as well as the nature of the substrate (mica) do not markedly affect the growth structures and orientation of the films deposited at this lower temperature.

The Structure of Metal Evaporated Tape

To investigate the structure of evaporated tapes used in magnetic recording, and particularly the possible presence of a surface oxide layer, several tape samples were fabricated by oxygen reaction oblique-incidence evaporation, varying the amount of reacting oxygen, and analyzed the sample structures by XPS, AES, and X-ray diffraction. It was found that the region near the surface is a mixed phase of metal atoms and oxides. These oxides changed from CoO to Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> +CoO, and then to Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , as the amount of oxygen was increased. However, intermixing of CoO with metal atoms is thought to contribute to the film durability.

Magnetic properties of thin films prepared by continuous vapor deposition

Magnetic thin films deposited by the oblique incidence evaporation are considered to have excellent characteristics for high density recording medium. The magnetic properties and microstructures of these films prepared continuously with a roll coater have been investigated. In continuous vapor deposition, two different modes of deposition processes are considered, corresponding to substrate running direction. The HIN (high incidence nucleation) direction implies that deposition initiates at higher incidence angle and shifts to lower incidence angle. The LIN (low incidence nucleation) direction is the opposite. Hc and Ir/Is of the films by HIN direction have larger values than those by LIN direction in the same region of incidence angle. According to TEM micrographs of thin films by HIN direction, it is observed that elongated nucleation is taken place in higher incidence angle direction and subsequently grown in same direction.

Recording and reproducing properties of magnetic tape by high incidence angle nucleation method

Application of the magnetic thin films prepared by the oblique incidence evaporation technique, named as "High Incidence angle Nucleation(HIN) method", to the microcassette music tapes has been investigated. To obtain the dynamic range at low frequency, it is required to increase film thickness of magnetic layer. However, the coercive force and the gradient of hysteresis curve, (dΦ/dH) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hc</inf> , of single layer film decrease as the film thickness increases after taking the maximum values at about 1000-1500 Å thickness. The multilayer films composed of A1 layers and Co-30%Ni layers being deposited alternately show the excellent magnetic properties. As-deposited multilayer films shows the large fluctuation in the reproduced output level which is the most difficult problem in the recording and reproducing properties of thin film medium. By polishing the film surface, it is improved and higher values of the reproduced output are obtained. These improvement are due to decrease of the spacing-loss between recording head and the magnetic film surface. The magnetic tapes prepared by the improved processes mentioned above, have the coercive force of more than 600 Oe and exhibit the recording frequency characteristics equal or more superior to those of the metal powder tape.

ホール効果を用いた一軸磁気異方性膜の磁化容易軸決定法

This paper proposes a new method to determine the direction of easy axis in a uniaxial magnetic anisotropy film using the extraordinary (or spontaneous) Hall effect. In this method, the magnetic easy axis is derived mathematically from two magnetic hard directions. The hard directions are obtained experimentally as the magnetic field directions where the Hall characteristic curve loses hysteresis. In order to examine the validity of the method, nickel thin films with oblique magnetic anisotropy were prepared by oblique incidence evaporation, and the Hall effect was investigated on these films, stressing on the field direction dependence of the Hall curve. The experimental results agreed well with the theoretical considerations. It was also found that the hysteresis disappearance was very sensitive to the direction of the applied field H particularly in magnetically well-oriented films. This fact suggests that the Hall method enables high accuracy measurement of the easy axis. Accuracy better than 0.1° may be expected by this method.

An electron diffraction study of oriented crystal growth in gold and copper films condensed in vacuum at oblique vapour incidence

Gold and copper films were condensed from a small source (at 30 and 20 AA s-1 where i=0) over a range of angles of incidence i from 0 to >45 degrees , in vacuum at defined pressures between 1*10-8 and 2*10-3 Torr, on flat glass and polished stainless steel substrates at room temperature. After the initial very thin random layer, growth developed in (111) orientation with its axis tilted by delta towards the vapour stream, and delta rose quickly from approximately 0 as deposition proceeded, at 5*10-6 Torr or lower becoming nearly constant at 4-6 degrees when i=45 degrees , for films >300 AA thick. There was little or no change in delta when additional (111) twinning occurred. When the later growth in (211) orientation was developed, delta immediately increased by about 20 degrees , to delta approximately 25 degrees , indicating its origin by (211) face development rather than by secondary (111) twinning which would have increased delta by only about 5 degrees . Observations at oblique vapour incidence are clearly important in establishing the origin of preferred orientations arising as films grow thicker. The relation delta approximately=ki leads to expressions of form K exp (-n phi 2/2) for the film-surface distribution function f( phi ) for the (111) oriented gold, with n/2=3.25 for films at 1*10-8 Torr, and n/2=7 for films at 5*10-4 and 2*10-3 Torr.

The structure and growth of thin films of CdS, CdSe and CdTe condensed in vacuum on to polished stainless steel substrates at room temperature

Polycrystalline films of CdS, CdSe, and CdTe up to 104 AA thick were condensed on to polished stainless steel substrates initially at room temperature in residual air at pressures from 5*10-3 to 10-7 Torr, at normal and oblique vapour incidence. Surface structures at a series of film thicknesses were determined by high-energy electron diffraction. Randomly disposed hexagonal crystals were observed up to a thickness H, at the surfaces of films condensed at residual air pressure p after which strong (0001) orientation was developed in the further deposition. At normal incidence H was approximately 1000 AA for p=5*10-3 Torr, and H rose with decrease in p, up to approximately 1500 AA at 5*10-7 Torr.

An X-ray diffraction profile analysis in hexagonal cadmium films vacuum-evaporated from normal and oblique vapour incidence

An X-ray diffraction profile analysis in hexagonal cadmium films vacuum-evaporated from normal and oblique vapour incidence