Banpil Photonics Reveals Methods of Forming Arrays of Nanoscale Building Blocks for Optical and Electronic Devices

Banpil Photonics, Inc. (Santa Clara, CA) earned U.S. Patent 7,662,659 for a method of producing an array, or multiple arrays of quantum dots. Single dots, as well as two or three-dimensional groupings may be created.  

According to inventors Nobuhiko P. Kobayashi and  Achyut Kumar Dutta the fabrication method involves the transfer of quantum dots from a receptor site on a substrate where they are originally created to a separate substrate or layer, with a repetition of the process and a variation in the original pattern to create different structures.  The manufacturing method can be used for fabricating wide displays, imaging devices, low threshold lasers, quantum confinement devices as well as other optical and electronic devices.

As the miniaturization of synthesized functional structures that possess electrical, optical and mechanical functionalities continues to progress rapidly, fabrication techniques based on conventional multi-steps of photolithography and subsequent etching processes appear to be approaching to their practical limits quickly. In the quest for discovering alternative techniques to such "top-down" approaches in which bulk materials are engraved into small-scale functional structures, the concept based on "bottom-up" approaches in which small-scale functional structures are formed by spatially arranging nanoscale building blocks, e.g. atoms and/or molecules, on given foreign substrates have been gaining significant attentions.

One of the bottom-up approaches that have been explored extensively in the past ten years is spontaneous self-assembled quantum dot, in particular, coherent, i.e. free from structural defects, small semiconductor inclusions, with a linear order of several tenths of nanometers, in a semiconductor matrix. However, inherent challenges associated with various formation techniques of spontaneous self-assembled quantum dots (SAQDs) have been hindering them from being prosperous approaches to synthesize small-scale functional structures.

As the term "spontaneous" indicates, the lack of control on specifically positioning SAQDs into densely-packed multi-dimensional periodic arrays has been a serious issue that needs to be aggressively addressed to ensure flexible tuning of physical properties of the small-scale functional structures consisting of SAQDs

           

Banpil Photonics solves the problem by providing technique to transfers uniformly distributed quantum dots to a separate substrate by which novel devices can be fabricated.  Kobayashi  and Dutta also developed a manufacturing process for  uniformly distributed quantum dots with preselected size-distribution and density on the flexible substrate for high performance novel devices.

A two-dimensional periodic array of nanoscale receptors is used as a template by which nanoscale building blocks are weakly captured. A two-dimensional periodicity of the template consisting of nanoscale receptors characterizes a two-dimensional periodicity of nanoscale building blocks captured by the array of nanoscale receptors.

The nanoscale building blocks weakly captured by the nanoscale template are subsequently physically transferred onto a foreign substrate by forming strong bindings between the nanoscale building blocks and the foreign substrate. The quantum dots being detached from the nanoscale receptors results in an array of nanoscale building blocks, having a two-dimensional periodicity characterized by the original array of nanoscale template, on the foreign substrate. This transfer technique can be repeated to form three-dimensional array of nanoscale building blocks.

The nano-scaled blocks can be quantum dots, atoms, or molecules on the substrate or the layer of the materials. For example, CdSe quantum dots can be formed using the organic receptor like protein template and can be transferred to the foreign substrate (e.g. ZnS) or to the layer of material (e.g. ZnS layer) to form the quantum dot based optical devices. Arrays of single layered quantum dots or three-dimensional quantum dots can be formed to enhance the device performance.   The methods permit the fabrication of  novel optical and electrical devices with significantly higher performances as compared with the bulk-based or non-uniform quantum dot based devices