#227 from R&D Innovator Volume 5, Number 7          July 1996

The Answer Came in a Dream
by Ijaz A. Rauf, Ph.D.

Dr. Rauf is a research scientist in the department of physics, Queen’s University, Ontario.

When someone asks me what was behind my invention of a superior thin film, I say it must have been part of a Divine design.  I began working on thin films at Punjab University in Pakistan.  Having done very well in my studies at Punjab University, I was awarded several fellowships and went to Cambridge University to pursue a Ph.D. degree, doing research on tin-doped indium oxide (ITO).  This material has properties that make it especially useful.  It reflects in the infrared region (heat radiation), absorbs UV, transmits visible light, and conducts electricity.  ITO is used in solar cells as well as flat-panel display devices such as laptop computers, digital watches, and calculators. 

My supervisor wanted me to study the mechanism that hinders electron passage in thin films of ITO. I surveyed the work in the field and concluded that the tin dopant atoms, which are introduced to generate mobile electrons, hinder electron passage through the material.  I suggested to my supervisor that the way to study this phenomenon is to produce a multilayer stack of alternating doped and pure indium oxide layers, so that electrons are produced in the doped layer and will then move freely in the undoped layer.  Therefore, if the electrical properties of the proposed multilayer structure are significantly improved, that would prove that the dopant is the dominating factor in hindering the path of the electrons.  If this layering experiment doesn't improve electron mobility, then the experiment would have eliminated one factor from the list of possibilities.

Unable to Follow My Own Plan

But my supervisor just smiled and said, "It's not that simple.  I suggest that you start depositing amorphous ITO films and study their microstructure and other properties."  The money funding my supervisor’s position came from industry, and it seemed that the kind of work was strictly specified.  Because of my strong religious background, I didn't argue with him, and began following his approach.  After a year of work, I wasn't able to achieve any significant results.  Again, I requested permission to pursue my original strategy; but my supervisor wouldn't relent.  We had an argument and he stopped supporting my work.  Fortunately, through my fellowships, I could still continue my research.  So now I was free of the industrial connection and pursued the direction I felt would be more important.

Couldn’t Repeat the Results

The first thing I did was to design and construct a substrate heater.  This was a simple apparatus, with wound metal wires (like in room heaters).  A thin mica sheet was placed over the coils, and a 4 mm thick copper plate was put over the mica sheet to produce a uniform temperature on the substrate surface.  This was important as a small variation in temperature may generate stresses in the films, and therefore adversely affect the film's properties.

Films were prepared by making a high-temperature vapor of ITO and allowing the vapor to deposit on a glass slide resting on the heated copper plate.  After each experiment, I had to take the heating apparatus apart for cleaning.

One day, I prepared a film that had electrical conductance four times greater than I had previously observed!  I couldn't believe these results, so I repeated the experiment, and was extra careful.  Unfortunately, I just couldn't make another film having that superior quality.  What was going on?

I showed the "superior" sample to my supervisor who was very impressed and sent it to Pilkington Brothers Ltd., the largest European marketer of coated glass.  They were also impressed and one of their physicists asked me how that particular sample was made.  I responded, "I don't know."  But my supervisor smiled, and said, "We'll try and reproduce the results."  I visited Pilkington Brothers and talked about my work.  Soon I received a generous check from them with a note stating that I had no obligations associated with accepting the money.  This was good timing, as I was in need of funds then to pay various university fees.

However, my supervisor began to put enormous pressure on me to tell him what I did that yielded those special samples.  As hard as I tried, I just couldn't figure out what I did different that day.  He became very angry and threatened that I would not get my Ph.D. unless I told him.  I felt that I had to report this to he department head who then tried to reconcile us.

I examined the microstructure of the superior film and showed that it was quite different, but we just couldn't understand how that structure was formed.  Soon after, however, my supervisor told me that he is responsible for knowing what I do, and if the situation doesn't change that he might lose his job.  He then threatened to prevent me from writing my theses unless I tell him how I made that film.  This put even greater pressure on me.  I could stand it no longer, so I spoke to the head of the microstructure research group.  He seemed to understand my predicament and gave me permission to write a thesis under his guidance.

The Answer Came in a Dream

About two weeks later I had a dream.  I saw myself getting ready to prepare a thin-film sample and, while putting the heater together, I picked up the copper plate and said to myself, "I don't need this, I'll put the substrate in direct contact with the heater coils."  Then, in the dream, I start evaporating the material, and saw the heater coils turn into red-hot brooms, sweeping back and forth.  I saw them drag the dopant atoms into certain regions.  The dream had a dramatic impact on me, so the next day I set up an experiment without the copper plate.  And guess what?  The resulting film had those superior properties!  Now I figured out what I had done in that first "successful" experiment.  My mind must have been on something else the day I did that “successful” experiment, as I must have forgotten to put the copper plate on the heater.  The ITO was deposited on the glass slide having strips of warm and hot temperatures resulting from the closeness of each heating coil.

It seems that the temperature gradients, in the absence of the copper plate, sweep the defects to the warmest side of each deposited ITO grain.  Because defects migrate the same way in neighboring grains, the lattices also become similarly aligned, and this property then dramatically increases conductance of the thin film.

After my Ph.D., I went to Queen’s University as a postdoctoral fellow to work on steels, a project having nothing to do with thin films.  My supervisor, however, graciously allowed me to pursue thin-film research in my spare time.  I developed better ways to engineer ITO grain orientation as well as to enhance crystal lattice alignment.  This work was going so well that I took a research scientist position with professor Michael Sayer, at Queen’s, to work full time on thin films.  We are developing a laboratory process into an industrially feasible technique for high-quality think-film deposition.

A few months ago, I presented my findings at the Material Research Society meeting in Boston, and was very pleased at all the attention my work gained.  I continue to wonder how that dream came about.  Perhaps a Divine reward for my strong belief in Islam?

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