Writing with Atoms

How can you see single atoms?
Atoms are the building blocks of every cell and every material. An atom is only about 0.3 nm in diameter. To “see” these atoms, you have to use special microscopes. The most famous one, is the AFM (Atomic Force Microscope), which I briefly described in my first post. This technique basically feels the atoms underneath it with a very very sharp tip, ideally so sharp that there is only one atom at the tip. The tip (called cantilever) is scanning slowly over the whole surface and creates a topographical image. Below you can see salt at atomic resolution. Each "dot" is one single atom, isn't that just amazing?

Salt (NaCl) atoms under an AFM.
The frame size is 5nm.
(Image taken from: Jessica Topple)

Who wrote with atoms first?
The first amazing demonstration and milestone of modern nanotechnology, was the fact that one can write and manipulate single atoms. This was first archived by Don Eigler from IBM in 1989. He successfully managed to arrange 35 Xenon atoms to write the famous letters "IBM" (see image below). This was realized with an STM (Scanning Tunneling Microscope) tip. An STM works very similar to an AFM, the main difference is, that the tunneling current between the tip and the sample is controlled and kept constant. With an AFM, the force between the atoms are measured therefore it works on non-conducting materials as well. 

IBM logo with 35 Xenon atoms. (Image taken from IBM) 

How do you write?

Don Eigler, who was the first to ever write with atoms, used an low-temperature ulta-high vacuum (UHV) system (check out my other post on Extreme Science). This system is required in order to have a super clean environment with no other disturbing atoms and to reduce the vibration of the atoms by lowering the temperature. The trick now to move an atom across the surface is to get very close to the atom with the STM tip. At some point, a positive van der Waals attraction between the atom on the tip of the STM and the atom to be moved is created, the atom is attached to the tip. Now by keeping this distance short, the atom can be moved to a different location. Once at the correct position, the STM tip just needs to be moved away from the atom and it stays put. In only 22 hours, the first IBM logo written with single atoms was created.

Why is it important?

First of all, it's fun and amazing! Second, it was the first ever approach for nanometer scale manipulation. Third, you can now move atoms to where you want them to be to create new structures.

Since then, many more universities, institutes and companies all over the world created atomic sized versions of their logo. Here are some cool examples:

Image by: NIST, USA

Image by: Technische Universität München, Germany

Image by: University of British Columbia, Canada

What is ‘Power of Minus 9’?

Power of Minus 9 is a nanotechnology blog which explains the beautiful, mysterious and inspiring world of life in the nano-scale and beyond. This blog intends to explain current nano-related topics to the curious, anxious, attentive future nerds and all others. I want to show you how awesome science can be. 

So, what exactly is the name ‘Power of Minus 9’ referring to? It is an allusion to the scale of a nanometer (nm), which is a billionth of a meter and in scientific terms written as 1*10^-9 m, which is 0.000000001 m, a loooot of zeros. This scale is really small, e.g. an atom has a size of 0.1 nm, only a tenth of a nanometer. Amazing, isn’t it? To show you how small a nanometer is, imagine a hair, which is roughly 0.1 mm thick, now cut it into 100’000 pieces then you end up with hair pieces that have a thickness of 1 nm. It’s like looking at stars, but the other way around. Instead of looking extremely far away, you’re looking to the other side of the scale, extremely zoomed in. 

What is all the hype about nano then, except that it’s incredibly small and hard to see, feel or imagine? Well, if you are dealing at this scale, you are trying to understand what single molecules, atoms and cells are doing. Quantum effects play an important role as well, particles do not behave like we used to know anymore. They start to exist at two different places at the same time, a lot of weird stuff is going on down there. Useful applications result out of nanoscience as well, like designing new electronic memories built out of single atoms to enhance performance and decrease size. A more futuristic idea is to fabricate a nano-sized small robot which navigates through your blood system and repairs the human body from the inside.

Principle of Atomic Force Microscopy (AFM). The cantilever scans over the surface. Due to forces between the atoms the cantilever will bend and a topography map is created.

What’s different about this scale is how to ‘see’ what you’re dealing with. With a microscope you can’t visualize single atoms; the resolution is by far not high enough. However, there exist several techniques, which allow you to see what atoms look like and are what they are doing. One of them is Atomic Force Microscopy (AFM). It’s a very powerful tool and actually a quite simple technique. You take a cantilever made of silicon, which looks like a long arm attached to a base. At the far end of the cantilever is a tip shaped like a pyramid. Ideally, this tip is very sharp with only one single atom at the end. The tip scans over the surface and senses individual atoms underneath. If there is a valley or a hill, the cantilever will bend towards or away from it. With a laser, which emits light onto the cantilever, the movement can be detected and a topographic map is created (see image). The AFM was invented in the 80s and opened the door to the nanoworld, as this was the first tool to imagine non-conducting surfaces at the nanoscale.

This blog will explain and discuss the latest development in the broader field of nanotechnology, trying to answer questions like, what does a quantum computer do? How does your cell phone camera works? What is a brain chip? What’s up with nanofluidics? and many more. Getting curious? All of these questions will be clarified in a simple but challenging way, so that everyone can have a piece of the awesome nano-cake. If you’re interested in a topic, leave me a comment and I will try my best to cover this in one of my next posts.