Self-assembled Nanodot Arrays Research Articles

Long Range Ordering of 5-nm-Sized Dot Arrays with a Pitch of <10 nm along EB-Drawn Guide Lines Using PS-PDMS Self-Assembly

We demonstrate the possibility of forming long-range-ordered self-assembled nanodot arrays with dots size of 5 nm and pitches of 10×7.5 nm2using guide line templates and low molecular weight (MW) (4,700–1,200 g/mol) poly (styrene)-poly (dimethylsiloxane) (PS-PDMS) for application in ultrahigh density patterned media. The self-assembled PDMS nanodots are controlled in a long range by varying the heights and gaps of the guide lines. Adopting the 14-nm-high resist guide lines with suitable gaps, the 5-nm-sized and 10×7.5 nm2-pitched self-assembled nanodots were ordered in maximum 7 dot arrays with long-range order. The experimental results demonstrate that the method is possible for achieving patterned media with magnetic recording densities of 8.6 Tbit/in.2using low MW PS-PDMS and slim guide lines.

Ordering of 6-nm-sized nanodot arrays with 10-nm-pitch using self-assembled block copolymers along electron beam-drawn guide-lines

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.

Attempts to form the 10-nm-order pitch of self-assembled nanodots using PS-PDMS block copolymer

Block copolymer (BCP) self-assembly exhibits its ability to form various nanostructures with a size down to 3 nm, which is particularly attractive for emerging technologies such as bit patterned media (BPM). Poly(styrene-b-dimethyl siloxane) (PS-PDMS) has been acknowledged as the most promising block copolymer for self-assembly fabrication due to its possibility to form nanopattern with a fine pitch, high etching selectivity, and its characteristic of robustness for pattern transfer. Here, we attempt to form PS-PDMS self-assembled nanodot array with a 10-nm-order pitch in order to satisfy the demand of low cost technique to form ultrahigh density nanodot array for BPM, which is regarded as the next-generation magnetic recording media, and for quantum devices such as the third-generation quantum dot photovoltaic cell and future battery cell. In this study, self-assembled nanodot array on a large area with pitches of 11 nm ( σ = 2.08 nm) and 10 nm ( σ = 1.61 nm) was formed using PS-PDMS with molecular weights of 5600–1300 g/mol (minority block volume fraction f PDMS = 19.8%) and 4700–1200 g/mol (f PDMS = 21.4%), respectively. In experiments, it was shown that some critical parameters, such as the thickness of PS-PDMS film, the treatment of the substrate surface, and annealing condition, played crucial roles in forming 10-nm-order size of self-assembled nanodot array using PS-PDMS. The relationships between pitches of PS-PDMS nanodot array and the product of the total number of segments and the Flory-Huggins segmental interaction parameter (χN) obtained by calculations and experiments will be discussed. Based on the position of PS-PDMS on mean-field phase diagram for BCP melts, the possibility to form nanodot array with a pitch of less than 10 nm is described. This study promises to open way toward the fabrication of more than 7.45 Tbit/in. 2 storage devices and the application of quantum devices.

Fabrication of CoPt Nanodot Array with a Pitch of 33 nm Using Pattern-Transfer Technique of PS-PDMS Self-Assembly

The progress of information technology has increased the demand of the capacity of storage media. Bit patterned media (BPM) has been known as a promising method to achieve the magnetic-data-storage capability of more than 1 Tb/in.2. In this work, we demonstrated fabrication of magnetic nanodot array of CoPt with a pitch of 33 nm using a pattern-transfer method of block copolymer (BCP) self-assembly. Carbon hard mask (CHM) was adopted as a mask to pattern-transfer self-assembled nanodot array formed from poly (styrene)-b-poly (dimethyl siloxane) (PS-PDMS) with a molecular weight of 30,000-7,500 mol/g. According to our experiment results, CHM showed its high selectivity against CoPt in Ar ion milling. Therefore, this result boosted the potential of BCP self-assembly technique to fabricate magnetic nanodot array for the next generation of hard disk drive (HDD) due to the ease of large-area fabrication, and low cost.

Fabrication of Carbon Nanodot Arrays with a Pitch of 20 nm for Pattern-Transfer of PDMS Self-Assembled Nanodots

We investigated the fabrication of self-assembled nanodot array using poly (styrene)-poly (dimethyl-siloxane) (PS-PDMS) block copolymer and its transfer technique as a promising method to fabricate magnetic nanodot arrays for ultrahigh density recording. A carbon (C) layer with a high etch-resistance was especially adopted for magnetic nanodot fabrication. We fabricated PDMS nanodot using PS-PDMS block copolymer with a molecular mass of 11,700-2,900 g/mol. The nanodots were first transferred into silicon (Si) layer and then into C layer on Si substrate by carbon tetrafluoride (CF4) and oxygen (O2) reactive ion etching (RIE), respectively. We succeeded in fabricating C nanodots with a diameter of 10 nm and an average pitch of 20 nm.

Orientation-Controlled and Long-Range-Ordered Self-Assembled Nanodot Array for Ultrahigh-Density Bit-Patterned Media

Orientation-Controlled and Long-Range-Ordered Self-Assembled Nanodot Array for Ultrahigh-Density Bit-Patterned Media

Orientation-Controlled and Long-Range-Ordered Self-Assembled Nanodot Array for Ultrahigh-Density Bit-Patterned Media

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.

Long-range-ordering of self-assembled block copolymer nanodots using EB-drawn guide line and post mixing template

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.

Novel Methods of Forming Self-Assembled Nanostructured Materials: Ni Nanodots in Al<SUB>2</SUB>O<SUB>3</SUB> and TiN Matrices

We have developed two novel methods of growing self-assembled nanodot arrays of uniform size (diameter 2-50 nm) of a variety of materials in crystalline as well as amorphous matrices. These methods employ a pulsed laser deposition technique and are classified as: (a) sequential growth method; and (b) simultaneous growth method. In the first method, the nanodots and matrix material are formed sequentially, while in the second method, nanodots and matrix materials grow simultaneously. In the sequential growth, self-assembly of nanodots is controlled by the flux of materials, interfacial energy, intervening matrix layer, substrate and laser parameters. For the simultaneous growth method of self-assembly of nanodots, there is additional requirement that the material of the nanodot and the matrix should be such that the Gibb's free energy of oxidation of the constituent of matrix material is much lower than that of the nanodot material.