Nanotechnology is the science of the very small, with researchers trying to construct objects on scales below a billionth of a metre across. One of the big challenges however is being able to figure out what you have built afterwards.
The constructs such as wires and novel materials are just too small to "see" in the ordinary sense of the word and new techniques are required to study what has been made.
A scientist originally from Skibbereen, Co Cork, and an undergraduate from University College Cork has been working on this problem for the last five years and has come up with a novel new imaging system that can literally read a surface atom by atom.
Prof J C Seamus Davis is professor of physics at Cornell University in upstate New York. He comes to Dublin next week to deliver two lectures, one for the Royal Irish Academy and another for University College Dublin. A key part of his talks will be about his imaging system that can see where all the atoms, impurities and holes are in novel materials, but can also read where the electrons are going when a charge is applied, the substances "quantum mechanical wave function", Davis explains.
"You don't care where the atoms are you want to know where the electrons are and what they are doing," he says.
"I came recently to this field but was intrigued to understand how the electronic structure is being altered at the atomic scale."
Being able to establish the physical make-up of a substance but also its wave function is a tremendous advantage to those making and trying to characterise new materials in nanotechnology.
The older methods involved what is known in the business as "shake and bake". You mix up varying amounts of the substances you want in your materials and then do batch after batch until you get one that does what you want it too.
"That process had very little information about what happened at the atomic scale," says Davis. "It slows down the development process a lot because you don't know what you did afterwards. The area I have pioneered is a different way."
His device allows scientists to make new materials and then to examine them in detail. "They can all be imaged directly," he says. "You make up your sample, you put it in the machine and you see what you made."
It is based on an existing technology, scanning tunnelling microscopy, but he has added the quantum mechanical data to this. "We can find every impurity, every atom. It really is like exploring."
It it a huge help when characterising a novel material and has helped Davis and his team to characterise new high temperature superconducting substances based on the "cuprates". These unusual substances were one of reasons Davis went into this aspect of physics. "The cuprates are one of the most outstanding problems in physics," he suggests.
There are several families but they all contain copper oxide. Superconductivity appears in the insulating copper oxide crystal planes of the cuprates when they are "doped" with tiny holes.
Davis's device can see the atoms but also the holes and can measure the electronic phenomena taking place in these doped structures.
Superconductivity was seen at remarkably warm temperatures, half way between absolute zero and room temperature.
Davis and his group recently began the first detailed studies of these phenomena in cuprate crystals which combine calcium chloride and copper oxide. His methods allow the group to make the crystals, view their topography and characterise the wave function, noting how the latter changes as the topography changes.
Dick Ahlstrom
Prof Davis delivers a general lecture at the RIA on February 7th entitled Visualising Complex Electronic Matter at the Atomic Scale. Further details are available at www.ria.ie. He delivers a scientific lecture, The Secret Order of the Cuprates at UCD on February 8th at 4pm. Both lectures are free of charge.