26 July 2011

If something is truly creative then it is invisible as such, since nobody else can recognise it to be so. If you tell everyone what they intrinsically know already, they will think you phenomenally astute and insightful. It’s a matter of perception, which is a strong force to try to break through.

20 July 2011

Elemental homeopathy

Yesterday I set out on a voyage to draw a picture of silicon. I had wanted to draw the silicon atom (and to subsequently work up to the crystal structure) whilst envisaging the positions of the electrons / their orbitals, as I wish to come to a degree of understanding about semiconductors; the freedom, or not, of electrons from the silicon atoms in its crystal lattice appears to be of some import in that regard. 

Semiconductors can conduct a little bit of electricity (more than insulators, less than metals) as a result of loosely bound electrons in their chemical structures that can be liberated by absorption of energy from the environment in the form of heat; with increasing temperature intrinsic semiconductors become more conductive. I had been reading about semiconductor doping, this being a mechanism whereby semiconductor materials (for example silicon) can be altered through the addition of tiny amounts of other chemicals (the dopants) in order to make them more conductive. It’s kind of like elemental homeopathy. The doping materials can either be such as to add electrons to the semiconductor, making it more negative and hence called n-type dopants, or to stick some of the free electrons that exist in the semiconductor more securely into the chemical structure, effectively making it more positive and thus called p-type. P- and n- doping are fundamental processes in silicon photonics where they are used on a precise and minuscule scale to manipulate the passage of current through chips and wafers, etc. I had been fascinated to read that the addition of a single arsenic atom per million atoms of silicon increases the conductivity of the latter by 100,000 times. The arsenic atom has one free electron that it lends to the process (it is an n-type dopant), and yet this tiny addition accounts for such significant changes in the behaviour of the material. And so off I set onto the sea of electrons.

My journey took me deep into the world of angular momentums and exclusion principles, illuminations of virtual photons lighting my way, as I floated on surfaces of identical electron particle/waves. I had a smooth crossing of the Dirac Sea, since there was nothing there to cause wind or heavy weather, although the negativity got hard to bear towards its infinitely distant shores. Luckily the outcome from such monotonous negativity can only be positive, and all of a sudden the antimatter positron popped into existence. I journeyed on through radiant matter, and passed a few anomalous magnetic moments. Many hours of incomprehension further into the books and pages, all the while trying to assess which bits of this science are knowledge and which are model. I know that people have focussed beams of electrons for one reason or another, but no one has ever actually seen an electron, so know not what they have focussed. I read words telling me that an electron has a mass of about 0.00000000000000000000000000009 g, has an electric charge of -0.00000000000000000016 coulombs and a spin of a half. But I am also informed that electrons have no substructure and are hence assumed to be a point particle with a point charge and no spatial extent. I’m not sure how I can draw no spatial extent.

In order to see anything it seems that we need an illumination source that has a shorter wavelength than the dimensions of the thing we are endeavouring to see. For example, we can see using light since it bounces off the surface of visible things in such a manner as to convey surface texture and colour of objects, etc., to our eyes. Using a classic light microscope we can visualise objects with a resolution of down to about a tenthousandth of a millimetre, at which point the wavelength of visible light is getting to be of a similar scale to what we are looking at and it ceases to be able to discriminate surface variations. With an electron microscope the smallest dimensions visible are in the low nm range, about a hundred or so times smaller than things that can be seen under a light microscope. In order to look at an electron or a photon we need (a) for them to have a physical existence, and (b) something that can visualise down to the range of their physical size. 

And so I am back at wondering how, in the name of Art, to depict silicon’s electrons. Mentioning my problem to M later in the day she suggests that I simply put forward blank sheets of paper, and since she is an Art Historian I think I’ll take her advice.

12 July 2011

tiny profiles

(i do like a palindromic date) 
Back in the lab. Briefly. I bumped into L in the corridor, and asked if she was going to be in the cleanroom, which she was, and so asked if I could accompany her, which I could. So I did. Her task of the moment was to measure the thickness of a film on a substrate. She hence coated said substrate, which looks extremely like a piece of glass (about 1.5 cm square) by adding her solution (a clear one, a couple of drops) and spinning it for 30s in a centrifuge-type machine. All of this took place in one of the clean boxes with her manipulating the sample and equipment via the arm-long black rubber gloves (they are the arm equivalent of thigh-high boots, but I cannot think what the word to describe them in that way would be. Were they boots they would be very kinky – stretchy, close fitting, limb-long rubber - but as gloves they are somehow so very prosaic. Nonetheless I cannot resist the temptation to see how it feels.). I put my arm into one of the gloves, fingers into inverted fingers then rolling into it from there up – already ensconced in two pairs of shoe covers, a full length Tyvek suit, two hoods, gloves and spectacles I felt somewhat encumbered. Goodness only knows how they conduct any subtle actions buried under so many layers. Prior to working on her sample L had to get it into the clean box, which requires it going in through a little evacuated ante-chamber. This chamber was flushed three times with nitrogen gas (that’s what is in the clean box), and then the sample moved into the chamber. She explained her process as she went along, and I struggled to hear amidst the rustlings of many layers of clothing and background machine noise. L is working with Ravi Silva, who is the director of the ATI, and who works (in part) on solar cells, his group exploring new materials and methods to make them more efficient, longer lived, smaller, etc. After the transparent fragment is coated with the transparent coating L removes the sample from the clean box and scratches the surface, in order to be able to measure the profile across it. This is undertaken using a profilometer. A profilometer is basically a probe that is dragged across the surface of something and which records the topography of the surface. I love that kind of technology; I imagine it to have been around for hundreds, maybe thousands, of years in almost the same form. The form of this one is somewhat twentieth century, being a rather fetching brown and beige computer-looking machine. On the label it says 1994, but to me it is reminiscent of a computer my dad bought in the early 1980s, all ergonomic curves and a small, embedded, flickery screen. Apparently it is so knackered that they can’t switch it off, and must simply turn the brightness and contrast down. L measures the profile and I get caught up in drawing the machine – as ever in the cleanroom I am restricted to using the shed-free paper and biros and pens. In the university shop on the way in to the lab I had stumbled upon a cherryade-scented pen, and so my drawing becomes a multi-sensual event. The profiling completed L must go to have a meeting with Ravi. We leave the clean room, disrobing in the ante-chamber as we flush back into the audible, unclean world.

5 July 2011

prime days


A prime date. 

5, 7 and 11 are consecutive prime numbers, but I wonder if 5,711 is one too? I guess the internet would be able to tell me in a flash. But I am not online at the mo. Somehow 5,711 does sound a suitably awkward number that it may be a prime. Let me see – is it divisible to an integer by 3? No. 5, no, don’t need to use a calculator for that. 7? No, but that’s a nice looking number 815.857142857142857142... 9, no. 11? No. 13, no. 15? No. 17, 19, 21, 23, 27? No, no, no, no, no. I’m beginning to wonder if I am going to have to try every odd number up into the hundreds...  maybe so. 35 (being a multiple of 7?) has a similarly good looking answer at 163.171428571428571428571... The forties and fifties and sixties give no integer divisible solutions, but the numbers by which they must be multiplied to get to 5711 are falling, and drop below 100. When I get up to trying 73 the answer is in the seventies, which means that I must be nearly there. 75? No, that is a 76.146666666666666666666666666666666666666666666666666666666667th of 5711. And so, seemingly all of a sudden, I know that it is indeed a prime day.

Last week a trip to the museum at Porthcurno whilst in the area to drop off a silicon photonics drawing. Porthcurno is a small bay on the south coast of Cornwall, down beyond Penzance, where, from 1870 onwards, early international and transatlantic telegraph cables crossed from the land into sea; submerged copper wires taking messages around the world. The first successful trans-Atlantic cable had been laid between the UK and USA in 1865. Submarine copper cables were insulated using gutta percha, a substance similar to rubber, which had recently been discovered. By 1900 Cornwall was connected to India, North and South America, South Africa and Australia via such cables at Porthcurno. Messages were transferred using Morse, or other coded systems; text messages being distributed via a global network more than a hundred years ago. 

And some interesting art. A piece called ‘Soundings’ by Penny Nisbet at the Porthcurno museum (http://www.porthcurno.org.uk/), in which audio signals are generated from a dormant, but largely intact, submarine cable, since it acts “as a giant antenna in the sea of electromagnetic waves we are continually immersed in”. She further says “The prospect of the ancient telegraph cable resting silently on the seabed adds something to the fascination of listening to the sound of the radio energy it is receiving, including natural radio emissions of cosmic and atmospheric origin as well as those from man-made power sources.”

At the nearby Newlyn Art Gallery I pop in to a related exhibition of sounds and sculptures, co-curated by students at Falmouth Art College, called Down There Among the Roots (see http://downthereamongtheroots.wordpress.com for more info). In the Lower Gallery the sounds, by Chris Watson, include those made by hydrophones submerged “at the point where the ocean breaks upon the land and burying equipment into the earth beneath a series of wires”. These noises accompany Phoebe Cummings’ un-fired clay sculpture in a vitrine (and I must admit I’m a sucker for a vitrine – if your tastes are of a similar vein take a look at Marielle Neudecker’s tank works sometime) of a scene incorporating Malaysian Isonandra Gutta trees, producers of the aforementioned gutta percha. Upstairs, larger miniature un-fired sculptures of the Cornish landscape are accompanied by sounds captured from stretched wires in Australia and Cornish field recordings. And the view from the cafe, it being a sunny, turquoise-seaed, cloud-rushingly breezy day, provides other sensory fulfilment.

Art, science and Cornwall on a sunny day – a prime combination.