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In this study, we investigated a parallel metal–insulator–metal (MIM) diode with an ultrathin spin-coated hydron silsesquioxane (HSQ) layer. Ti and Au were adopted as the metal electrodes for the large work function difference. Conditions to obtain the ultrathin HSQ layer with a thickness of below 5 nm for tunneling were predicted and Ti/HSQ/Au diode devices with a parallel electrode arrangement were fabricated by using the conditions. The typical current–voltage characteristics of the fabricated diodes exhibited asymmetry of about 1.8 at 3.0 V. It was demonstrated that the dynamic zero bias resistance of the diodes was as low as about 8 MΩ. Based on the Simmons model, the estimated oxide-equivalent thickness of HSQ in the device was about 1.7 nm, which was in good agreement with the prediction. The good figures of merit of the fabricated diodes imply that the spin-coated ultrathin HSQ is very suitable for this application.

Graphical abstractDisplay Omitted We succeeded in ordering 6-nm-sized dot arrays with 10-nm-pitch between guide lines.The ordering was achieved by graphoepitaxy with self-assemble and the line template.3 to 7-ordered PDMS dot arrays were formed between 12-nm-wide EB-drawn guide lines.The block copolymer was PS-PDMS with a molecular weight of 7000-1700kg/mol.The 10×12-nm-pitched nanodot arrays corresponds to 5 Tbit/in2 magnetic storage. We studied the possibility to form long-range ordering of self-assembled nanodot arrays with a dot size of 6nm and a dot pitch of 12nm using guide-line templates for ultrahigh-density patterned media. This was realized by using self-assembled block copolymers of polystyrene-poly dimethyl siloxane (PS-PDMS) and the templates made of hydrogen silsesquioxane (HSQ) negative electron beam (EB) resist. We have demonstrated that the method could possibly achieve a minimum pitch of about 10nm using PS-PDMS of molecular weight 7000-1500g/mol and EB-drawn guide lines. These results evidence the promising potential of a technology for achieving 5 Tbit/in2 magnetic storage devices.

We investigated the possibility of ordering of 12 nm pitced self-assembled nanodots from block copolymer (BCP) improved by the guide pattern with low line edge roughness (LER) for patterned media. We found that LER of the line pattern (σ-value) was reduced by using high-resolution salty development for HSQ resist line pattern fabrication compared with conventional tetramethyl ammonium hydroxide (TMAH) developer. By adopting this development technique to guide pattern fabrication, we demonstrated 10 rows of ordered self-assembled BCP nanodot arrays with a size of 6 nm and a pitch of 12 nm (5 Tbit/in.2) between the guide patterns.

A possibility to fabricate nanodot arrays with a dot size of 2 using self-assembling with PS-PDMS of molecular weight 7000-1500 and EB-drawing for narrow guide lines. These results prove that the fusion method is required for achieving extremely small dot arrays as 5 Tbit/in2magnetic storage devices.Keywords: Nanodot, self-assembly, electron-beam drawing, graphoepitaxy, patterned media, magnetic recording.

CoPt magnetic dot arrays with a fine pitch of 30 nm have been fabricated using electron beam (EB) lithography and ion milling. The possibility to ion-mill CoPt film using EB drawn calixarene resist pattern as a mask has been studied. We formed 30 nm pitch resist dot arrays with a dot diameter of 20 nm using 30-keV-EB lithography with calixarene resist. The resist dot arrays were ion-milled for 4 min using 200-eV Ar ion milling to fabricate CoPt dot arrays on a Si substrate. We fabricated fine pitched CoPt magnetic dot arrays with a diameter of 22-35 nm and a pitch of 30-150 nm. Results show that the ion-milled CoPt dot diameter increased with the dot pitch while the resist dot had a similar diameter of 20 nm.

In this work, improvement of the observation contrast was investigated by using a carbon film as the hard mask for pattern transfer of block copolymer (BCP) nanodots. The PS-PDMS (Poly (styrene-b-dimethyl siloxane)) block copolymer was adopted here. The observation contrast was greatly improved after transferring block copolymer (BCP) nanodots pattern to the underlying Si substrate through the carbon hard mask compared that before nanodot pattern transfer. Pattern transfer was also demonstrated to be very effective using carbon hard mask.

We investigated the effect of ultrahigh-resolution salty (NaCl contained) development of hydrogen silsesquioxane (HSQ) resist on forming fine dot arrays with a pitch of 15×15 nm2 by 30-keV electron beam lithography for patterned media. The optimized concentration of resist developers was determined to fabricate most packed pattern. We found that increasing the concentration of NaCl into tetramethyl ammonium hydroxide (TMAH) could greatly improve the resist contrast (γ-value) of HSQ. And by using 2.3 wt% TMAH/4 wt% NaCl developer, we demonstrated 15×15 nm2 pitched (3 Tbit/in.2) HSQ resist dot arrays with a dot size of < 10 nm.

We have studied the possibility to form fine magnetic column arrays using 30-keV-electron beam (EB) drawing with thin calixarene resist and 200-eV-Ar ion milling, and nanometer-sizing effect of the magnetic column on the corecive force for patterned media. We achieved 20-nm-sized resist dot arrays on PtCo magnetic and thin metals layers on glass substrate. We formed fine magnetic column arrays with a diameter of 39 to 106 nm and a space of about 100 nm using the resist pattern by the 200-eV Ar ion-milling. Using the nano magnetic column arrays, the hysteresis were measured by X-ray magnetic circular dichroism (XMCD) with an energy of 11.57 keV, which corresponds to an energy edge of Pt-L3. It is clarified that a coercive force of the nanometer-sized magnetic column increased as the diameter decreased.

We have studied functionalization of guide pattern with brush treatment. Especially, the effect of brush treatment on ordering of nanodots formed on the guide pattern was investigated. We used polydimethylsiloxane (PDMS) as brush modification to form self-assembled nanodots on the guide pattern using polystyrene (PS) - PDMS as block copolymer. The brush treatment using toluene solvent made guide patterns of the electron beam (EB) drawn resist behave like PDMS guide patterns and good ordering of the nanodots has been achieved. It was demonstrated that the brush treatment enabled the PDMS nanodots to be regularly located in the desired positions defined by the EB drawn guide patterns.

We studied long-range ordering of self-assembled nanodot arrays for patterned media, using a guide post and line mixing template made of an electron beam (EB) resist to pack many nanodot arrays between guide lines. We designed the mixing pattern, EB-drew it on silicon substrate, brushed the surface of the pattern, and self-assembled block copolymer dot arrays using polystyrene-polydimethl siloxane (PS-PDMS) and mixing templates made of hydrogen silsesquioxane (HSQ) negative EB resist. The experimental results demonstrate the possibility of forming long-range ordering of 6 and 9 self-assembled nanodot arrays with a size of 20nm and a pitch of 33nm between the guide lines, using the mixing templates with three and fourfold post lattices, respectively.

In this paper, we report two kinds of guide patterns precisely created by electron beam drawing. These guide patterns are expected to precisely control the arrangement of nanodots self-assembled from block copolymer (BCP) in order to obtain long-range-order nanofabrication. The first guide pattern is comprised only of a post lattice. The second guide pattern adds guide lines to the post lattice. The added guide lines are expected to better control the location and orientation of the BCP nanodots. We succeeded in fabricating these two kinds of guide patterns for 22-nm- and 33-nm-pitch BCP nanodots.

In this study, we investigated the possibility of forming the fine Si dot arrays by means of electron beam (EB) lithography and dry etching technique for the future’s devices with nano-scale structures. We examined the properties of Ar ion milling for the fabrication of nanometer sized Si dot arrays on a Si substrate. We have succeeded in forming 40 nm pitched Si dot arrays with a diameter of

Defects and their annealing behavior for low (2×1015/cm2) and high (1.7×1018/cm2) doses of 180 keV oxygen-implanted silicon have been investigated by the coincidence Doppler broadening (CDB) and lifetime measurements in variable-energy positron annihilation spectroscopy. In the low-dose sample, divacancies are induced throughout the entire implantation region. In the vacancy-oxygen coexisting region (300–500 nm depths), by raising the annealing temperature to 600 °C, vacancy–oxygen VxOy complexes with one vacant site are formed and, simultaneously, the migration of oxygen begins to takes place. In the vacancy-rich region (−200 nm depths), the evolution of simple vacancy clusters to V4 is mainly observed below 600 °C. From CDB and lifetime measurements, it has been proven that after annealing at 800 °C, the VxOy complexes are formed throughout the implanted region and they contain four vacant sites and a high ratio of y to x. On the other hand, high-dose implantation at 550 °C produces the VxOy complexes w...

Silicon (1 0 0) wafers have been implanted with 1×10 15 He + or Ar + ions/cm 2 and the vacancy (V)–He or –Ar complexes induced have been investigated with positron lifetime and coincidence Doppler broadening measurements using a positron beam. He + ion implantation into Si gives rise to formation of V 2 He complexes, which are transformed into V x He y ( x – y =1) complexes by annealing at 300°C. The amorphous phase induced by Ar irradiation of Si is transformed into a crystalline phase around 700°C. The crystallization accompanies formation of V–Ar complexes with six vacant sites, and these complexes are found to be stable above 800°C. These results have proved that positrons are very useful probes to study the chemical state of vacancy-inert gas atoms complexes.

Coincidence Doppler broadening (CDB) method in positron annihilation spectroscopy has been applied to chemical state analysis of the defects in silicon and iron implanted with O + 2×10 15 /cm 2 at 180 keV and Cu + 1×10 15 /cm 2 at 140 keV, respectively. Oxygen implantation to Si followed by annealing leads to the formation of vacancy–oxygen complexes. In combination with lifetime measurement, it has been found that V 6 O 2 complexes are formed by annealing at 600°C and transformed into V 10 O 6 at 800°C. In Cu ion implantation to Fe, it has been directly proved that vacancies and Cu atoms aggregate and our measurements suggest that the inner wall of the grown-up defect is covered with Cu atoms.

Variable-energy positron annihilation spectroscopy (VEPAS) has been extensively applied to study defects in near-surface regions and buried interfaces, but there is an inherent limit for depth resolution due to broadening of the positron implantation profile. In order to overcome this limit and obtain optimum depth resolution, iterative chemical etching of the sample surface and VEPAS measurement are employed. This etch-and-measure technique is described in detail and the capabilities are illustrated by investigating the depth profile of defects in Si after B and P implantations with 2×1014/cm2 at 100 keV followed by annealing. Defect tails can be accurately examined and the extracted defect profile is proven to extend beyond the implanted ion range predicted by the Monte Carlo code TRIM. This behavior is more remarkable for P ion implantation than B, and the mass difference of the implanted ions is strongly related to it. No significant difference is recognized in the annealing behavior between B and P i...

Two-detector coincidence measurements of the Doppler broadened annihilation spectra with a variable energy positron beam are carried out for the study of the annealing behavior of Si implanted with As, P and Cu ions. Different annealing behaviors are observed depending on the ions implanted. In P implanted Si, defect complexes grow in the temperature range up to 400 °C. In case of Cu implanted Si, the formation of vacancy-Cu complexes is indicated. Coincidence Doppler broadening (CDB) measurement is a powerful tool for investigation of defects. Though, combination with other techniques is necessary for full utilization of CDB measurements.

A rapid prototyping system using a digital micromirror device (DMD) has been developed. A DMD is a micro mechanical light modulator with tilting mirror elements. In the developed system, the DMD and a mercury lamp are used as the pattern generator and the UV source, respectively. Since the developed rapid prototyping system does not require a mask or LASER, a simple, low-cost system can be realized. An exposure pattern modulated by the DMD is projected on the saface of the UV resin, and a hardened layer with the same shape as the exposure pattern projected on the resin surface is produced. The model can be constructed in any size by changing the optical magnification. By using illuminance compensation technique, both illumination non-uniformity and excess growth are improved. The model vibration system has been introduced in order to reduce leveling time of the resin. The rapid prototyping system using the DMD is highly cost-effective.

Interesting features of positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) distribution for singly negative divacancies in Si are studied experimentally and theoretically. Anisotropy of the distribution is successfully detected for a specimen with aligned divacancies and is well reproduced by first-principles calculations based on the two-component densityfunctional theory. The present calculation demonstrates that the anisotropy reflects the characteristic distribution of electrons around the divacancies, indicating that the 2D-ACAR is an effective tool to provide microscopic information on vacancy-type defects. [S0031-9007(97)02701-4]

The 26S proteasome has an elaborate structure, consisting of 33 different subunits that form the 20S core particle capped by the 19S regulatory particle on either end. Several chaperones that are dedicated to the accurate assembly of this protease complex have been identified, but the mechanisms underlying proteasome biogenesis remain unexplored so far. Here we report that core particle assembly becomes less efficient if the TRC pathway, which mediates insertion of tail-anchored proteins, is defective. We demonstrate that Bag6, a protein in the TRC pathway that is also responsible for the degradation of mislocalized proteins, is not only involved in core particle assembly but also has a key role in efficient regulatory particle assembly by directly associating with precursor regulatory particles. These findings indicate that proteasome assembly is not solely mediated by dedicated chaperones but also depends on general chaperones that preserve protein homeostasis.

Bit patterned media (BPM) is a promising candidate for next-generation magnetic recording media beyond 2.5 Tb/in2. To realize such high-density patterned media, directed self-assembling (DSA) technology is a possible solution to form fine dots. In order to read and write magnetic signals on a magnetic dot of magnetic media, the position of magnetic dots must be controlled. We examined ordering of directed self-assembly of diblock copolymer dots with a variety of prepatterned guides in some conditions and evaluated the ordering of the dots by using Delaunay triangulation and Voronoi diagram. Applying the optimized conditions, we obtained highly controlled dot pattern suitable for magnetic recording media.

We demonstrated the possibility to form long‐range‐ordered and self‐assembled nanodot arrays with a dot size of 20 nm and a dot pitch of 33 nm× 28nm using guide post lattice and line mixing templates for ultrahigh density patterned media. In the experiments using self‐assembled block copolymer of poly styrene‐poly dimethl siloxane (PS‐PDMS) and the mixing templates made of HSQ negative electron beam (EB) resist, we obtained the useful results that the templates permitted to form long‐range‐order nanodot arrays with larger margin of the post pitch deviation than that using 2‐dimensional post lattice and only guide line template. The result indicated the possibility to form 13‐nanodot arrays between guide lines using the mixing template.

A production method for a positron microprobe using a beta+-decay radioisotope (22Na) source has been investigated. When a magnetically guided positron beam was extracted from the magnetic field, the combination of an extraction coil and a magnetic lens enabled us to focus the positron beam by a factor of 10 and to achieve a high transport efficiency (71%). A 150-nm-thick Ni(100) thin film was mounted at the focal point of the magnetic lens and was used as a remoderator for brightness enhancement in a transmission geometry. The remoderated positrons were accelerated by an electrostatic lens and focused on the target by an objective magnetic lens. As a result, a 4-mm-diameter positron beam could be transformed into a microprobe of 60 microm or less with 4.2% total efficiency. The S parameter profile obtained by a single-line scan of a test specimen coincided well with the defect distribution. This technique for a positron microprobe is available to an accelerator-based high-intensity positron source and allows 3-dimensional vacancy-type defect analysis and a positron source for a transmission positron microscope.

We have studied the electronic structure of MnO by photoemission spectroscopy. Mn 3d--derived emission is found to be confined within \ensuremath{\sim}10 eV of the top of the valence band, and we find no evidence for an intrinsic satellite at higher binding energies. The photoemission intensity of the whole valence band is enhanced for photon energies in the Mn 3p\ensuremath{\rightarrow}3d core absorption region. These observations suggest that ${\mathit{d}}^{4}$ and ${\mathit{d}}^{5}$L photoemission final states (L denotes a ligand hole) are close in energy and are strongly hybridized with each other. The spectra are analyzed in terms of configuration-interaction theory using a ${\mathrm{MnO}}_{6}$ cluster model. We thus find that the ligand-to-Mn d charge-transfer energy \ensuremath{\Delta} is comparable to the intra-atomic Coulomb energy U\ensuremath{\simeq}7.5 eV. Namely, MnO is indeed close to the boundary between the Mott-Hubbard (U) and the charge-transfer (Ug\ensuremath{\Delta}) regimes in the Zaanen-Sawatzky-Allen phase diagram, and the ${\mathit{d}}^{4}$ and ${\mathit{d}}^{5}$L states are nearly degenerate. The large \ensuremath{\Delta} value leads to a highly ionic character in the Mn-O bonding.

Lifetime and Doppler broadening S parameter measurements using variable-energy positrons have been applied to Si implanted with $1\ifmmode\times\else\texttimes\fi{}{10}^{15}$ ${\mathrm{He}}^{+}/{\mathrm{cm}}^{2}$ at 60 keV. Two kinds of defective layers are compared: a vacancy-rich region in the near-surface layer less than 300 nm from the top surface, and a He-vacancy-coexisting region in the He implanted layer of 300--600 nm depth. In order to enhance the depth resolution of the positron beam spectroscopy, the positron measurements have been combined with a controlled removal of thin layers of the sample by chemical etching. For the as-irradiated sample, the predominance of divacancies in the near-surface layer is indicated. In the He implanted layer the defects are identified as divacancies coupled with He. Annealing of the samples at 300 \ifmmode^\circ\else\textdegree\fi{}C results in a diffusion of He atoms and a passivation of divacancies by He even in the near-surface layer. Upon annealing at 500 \ifmmode^\circ\else\textdegree\fi{}C, He atoms effuse completely from the sample and ${V}_{2}\ensuremath{-}\mathrm{He}$ complexes are transformed into ${V}_{4}.$ The vacancies decorated with He become positron trapping sites and the stability of He-related defects strongly depends on the formation of larger vacancy clusters.

Extraction of slow positrons from a guiding magnetic field was investigated experimentally. With moderate acceleration, more than 40% of slow positrons could be collected in the field free region. Experimental results indicated that minimization of the magnetic field around a moderator and precise alignments of an accelerating electric field with the guiding magnetic field were important in order to attain high extraction efficiency.

In this study, we investigated the control of the orientation and ordering of self-assembled nanodots from a block copolymer (BCP) with the help of a guide pattern created by electron beam (EB) drawing. The guide pattern consisted of a post lattice and guide lines. The former is used to enable self-assembled nanodots from the BCP to be regularly arranged, while the latter is used to control the orientation of the nanodot arrays. It was demonstrated that the combined guide pattern was effective for controlling the BCP dot array to achieve long-range ordering and controlled orientation.

A zero-bias resistance peak appeared in the tunneling resistance curve of Bi-cuprates, Na0.89WO3 and ReO3, contacted with GaAs or SnO2-x . Therefore the peak is not inherent to high-T c superconductors and may not be relevant to the electronic properties in the bulk.

A corner of a ReO3 single crystal was used as the tip for scanning tunneling microscopy (STM). The atomic arrays of graphite and ReO3 were easily observed. The image of the emissive area is round in the former and polygonal in the latter, reflecting, perhaps, the electron distribution in the uppermost band.

Positron lifetime spectra were measured at 20°C in Gd-doped BaTiO 3 which contained a large amount of Ba 2+ vacancies. It was found that the intensity of long-lived (τ 2 ) component was proportional to the nominal vacancy concentration and the averaged annihilation rate decreased as the concentration increased. To explain the observed results a model is proposed in which most of Ba 2+ vacancies form pairs with Gd 3+ and these pairs attract, but do not trap positrons, and isolated Ba 2+ vacancies trap positrons giving τ 2 component.

Rotating-specimen measurements of the annihilation radiation have been carried out to investigate the Fermi surface of α Cu-Al alloys up to 15.5 at % Al. The conventional angular-correlation measurements along the [100] axis have also been performed in a long-slit geometry. The Fermi surface of α Cu-Al alloys has been found to be similar in shape to that of Cu. A trend of the monotonical increase with Al concentration has been found both in the size of neck and in the Fermi momentum. The change in the Fermi surface of this alloy follows closely that of α-brass with the same e / a .

Infrared transmission spectra of metallic ReO 3 film deposited upon silicon plate have been measured in the region from 1200 to 30 cm -1 . Two structures are observed at 905 and 315 cm -1 at room temperature and assigned to the infrared active lattice vibrations of ReO 3 crystal. The force constants derived from the elastic constants support these assignments. Raman spectra of ReO 3 crystal were also measured and the results are consistent with those of infrared transmission. These results are compared with those of other transition metal oxides. Natures of the optically active lattice vibrations and the metal oxygen bonds in metallic ReO 3 are discussed.

Anisotropic distribution of the collinear pairs of photons from positron annihilation in a Cu single crystal has been measured around the axis with a conventional long-slit system. A method for the evaluation of the neck radius of the Fermi surface from the slope of the counting rate of the collinear photon pairs plotted against the azimuth angle around is presented and has been applied to Cu as a test case. The neck radius of Cu thus determined has been found to agree with that given by Halse. The observed anisotropy is larger than that expected from the topology of the Fermi surface with a Wigner-Seitz evaluation of the higher momentum components. This result suggests the anomalous enhancement of the annihilation rate of the neck electrons.

X-ray and ultraviolet photoemission spectroscopy (XPS and UPS) measurements are reported for ReO 3 . Difference between the XPS and UPS spectra has revealed O 2 p -derived non-bonding levels and Re 5 d -O 2 p bonding levels, confirming covalency effects in ReO 3 . A self-consistent-field-Xα-scattered-wave calculation on a ReO 6 cluster is presented and is compared with experiment. Effects of Madelung potential on orbital energies of the cluster are discussed with relation to covalency.

The angular distributions of photon pairs from positrons annihilating in ReO 3 single crystals were measured along three principal crystallographic directions. The observed curves showed marked structures and anisotropies. A comparison with simple models indicates that main features of these structures and anisotropies can be attributed to the shape of the Fermi surface and the higher momentum components which reflect t 2 g character of the conduction electrons in this compound.