Tuesday, January 30, 2007

Hi, Belgian. Hi, Ghent

I am excited and happy to find that one belgian guy visited my blog this morning. U are the first unknown foreinger visited my new blog after establishing it. Thanks for your visiting and welcome more friends here!

Now i want to introduce the research work of a student, S. Mahieu, from Ghent universit, Belgium. one man i also admired very much, not only because he published an excellent invited review on SZM (stucture zone model, specially for sputtering) as a student but his insight and independent thought.

As for his main opinion, u can glance over the graph below, and the details can be refered to the article: "Biaxial alignment in sputter deposited thin films" by S. Mahieu et. al at http://dx.doi.org/10.1016/j.tsf.2006.06.027 .



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Monday, January 29, 2007

Different shape, Same principle


Recent years one "new" sputtering technique has also emerged (see the attached text below), which was proposed by several vacuum companies in the different shapes but same principle. It seems like a diode sputtering except for combinating with an external ion soure.

It is well known that the diode sputtering suffer from the low ionization efficiency which result in high voltage and low deposition rate. So this technique was almost abandoned after the invention of magnetron sputtering several decades ago. although the magnetron sputtering technique have the advantage of higher local ionization, low cathode voltage, and high deposition rate, etc., it subjects to the low target utiliztion "racetrack" originated from the confined plasma (所谓成也萧何,败也萧何, 呵呵). Various efforts mainly by rotating the magnet or target have been adopted to improve the utiliazition, from the typical <30%>90%) target utilization. Of course, one coin has two sides. u should pay the addtional cost for the plasma soures, and it is suitable only when the benefit u gain can offset the added cost.

Anyway, we can get some beneficial inspiration from this example that 1+1>2, and we should rethink the techniques look like outdated. Something is bad in certain condition but it maybe become good under another condition. BTW, i think the configration of PQL is more reasonable than that of 4Wave. Do u think so? -__- .



"4Wave was founded in August 2000 by senior technical and management staff of the former Commonwealth Scientific Corporation (CSC), a leading manufacturer of ion beam sources and equipment acquired by Veeco Instruments in May 2000. The company's founders are the world's leading experts in ion beam deposition processes, and have developed the first-ever ion beam deposition production system, still in use by IBM for its most advanced product offerings. Our multidisciplinary staff bring an average of 15 years of experience in electrical, mechanical, software, process and system engineering. Sami Antrazi, President, has more than 12 years of engineering management and customer development experience. His professional career combines managerial, business development, and technical expertise in the capital equipment industry. Prior to joining 4Wave, he directed the electrical, mechanical, and software engineering departments at CSC. He also conducted advanced robotics research for space applications for three years with NASA's Goddard Space Flight Center. He holds a Ph.D. (ABD) and an M.S. in electrical engineering from Catholic University in Washington, D.C."

http://www.4waveinc.com/ds.html



"Plasma Quest Ltd (PQL) founded by Professor Mike Thwaites in 1998 is a problem solving research-based company whose core business is thin film deposition sputtering research, and systems development. PQL has developed a high-density plasma method of thin film sputtering that provides process and thin film deposition benefits not currently available from conventional systems - the patented technology, “High Density Plasma forming device” is operationally referred to as High Target Utilisation Sputtering (HiTUS)."
http://www.plasmaquest.co.uk


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Strange doctoral dissertation!

These days i found several strange Phd theses on the website of the Plasma & Coatings Physics group of Linkoping University, Sweden. <http://cms.ifm.liu.se/materialphysics/plasma/publications/>.

At a glance, the length of the dissertation is abnormal short compared with that we usually see, ranging from 40 to 70 pages, and there are few experimental data or graph through the text although it also divived into several chapters. They just gave out the list of their published papers in the beginning of the thesis. Thus, these dissertations look like a review rather than a normal thesis. Prof. Helmersson's group is a reputed group in thin film technology, especially in HIPIMS which is the lastest generation of magnetron sputtering technique and originated from this Lab in 1999. Why do they choose the abnormal arrangement, "a review" instead of "a thesis"? I think that it is of advantaged to give the reader a integral development of this field, clear exhibit their contributions to this field, and let us know what has been done, what they did, and what should do in the future. Of course, maybe we have the courage to take this form only when we are sure that we contributed to one field indeed.
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Sunday, January 28, 2007

Memo for my first paper

My first two papers have been published online this month with some kind friends' help. It is a little shame for me to say it, because it take me over three years to achieve this course, and many my classmates have already published a long list of good papers until now. However, i learned a lot from the course. Now i want to have a conclusion and share some with others.

1> Avoid to publish the paper for the sake of publishing itself as possible. We will not feel any happy but depressed at last if one day we found that our paper had no any indeed contribution to our field. Unfortunately, i also did bad in it before, so it is my lesson.
2> Design and consider the experimental details before beginning it.
3> Put emphasis on the analysis of data, and be sure of their accuracy. As for how to get a beautiful graph, we can refer to one excellent PPT "how to deal with the data".
4> Learn some scientific writing skills. The details may be refered to some excellent articles such as "how to write a paper" by a professor of Cambridge.
5> Put the draft on the desk and revise it several weeks/months later. Alternatively, send it to others for the review if possible before the post.
6> Be concise as possible. One common problem for the freshman like me is that we used to stack all that we know not the new finding.
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If you have interest in my papers, you can reach it at the following address:

X.B. Zhang, Z. L. Pei, J. Gong, C. Sun, “Investigations on the electrical property and inhomogeneous distribution of ZnO:Al thin films prepared by dc magnetron sputtering at low deposition temperature”, J. Appl. Phys. 101, 014910 (2007). [Link][Full Text].

[ It is a developing trend to deposite thin films and fabricate the device at the lower processing temperature, the same to the preparation of TCO films such as AZO by magnetron sputtering. However, there are still some difficult problems to solve that the properties of TCO films are severe degraded and inhomogeneous under the low temperature processing conditions. Although many researcher have already investigated it, there are not a clear and consistent explaination on the origin of the inhomogeneity in the literature. This paper was aimed to clarify the two existing main opinions and deduce some feasible methods. I ever thought that my opinion was undoubtable. Now i think that i should do more experiment and give more sufficient evidences to support the viewpoint because we used to trust in our own opinion too easy and hardly oppugn it, although i don't think my opinion is wrong until now. ]

X.B. Zhang, J. Q. Xiao, Z. L. Pei, J. Gong, C. Sun, “Influence of external solenoid coil arrangement and excitation mode on plasma characteristics and target utilization in a DC-magnetron sputtering system”, J. Vac. Sci. Technol. A 25, 209 (2007). [Link] [Full Text].

[The improvement of target utilization and the independent control of plasma growth parameters are still two critical issues and worth concerning further. However, the research objective of this paper is a gradually outdated and abandoned technique (this method appeared in the beginning of 1990s). Therefore, it is more wise to do research on the promising technique; but i had no wide enough eyeshot and deep understanding on this field in the beginning. Of course, hope that there are still few useful elements existed in it. ]

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Saturday, January 27, 2007

Goal of this blog

The main purpose to set up this blog is aimed to practise and improve my written English. Another function is to record some personal thought or special information, mainly involved in my work. Thus, i will greatly appreciated it if u would like to point out my English error and give me some advice/comments.

Well, i almost forget the last and funny one that i hope one day the lamps would light all overthe world map :) , although there are only two lamps in the map as shown below:



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Friday, January 26, 2007

TCO niuniu in my eyes (1) ---- K. Ellmer


Results found:60 Sum of the Times Cited :819 Average Citations per Item : 13.65 h-index :17




















In my eyes, Dr. Klauss Ellmer is one of admiring scientists in the area of TCO (transparent conducting oxide) films, especially Al-doped ZnO films (AZO) by magnetron sputtering. Now he work in the solar energy division of Hahn-Meitner-Institut Berlin as a senior researcher. According to the statistic of ISI web index (up to 2006), he authored only 17 papers about AZO films in the last decade. However, the total of cited number is over 340 times, approximately 20 times per paper. Maybe somebody think that the number is just so so, but it is considerable if we take into account that the research on AZO films by magnetron sputtering has been intensively carried out by numerous groups, and not achieved a great breach in the last two decades.
His main contribution to this field is correlating the plasma parameters with the microstructure, electrical, and optical properties and having a systemtic investigation on AZO films using this method. We often found that the results of diffirent authors in the literature conflicted each other even though they used the same preparation method, same external parameters. This make us lost! and it is difficult to make a clear and reliable correlation between the process conditions and film properties. Therefore, his approach, probably inspired from the classic work on TiN coatings by Petrov group (another pioneer i admired will be introduced in later articles ), is more insightful and necessary for a better understanding of TCO materials.

In the last years such an approach was reported only on few papers, in order to achieve further progress in understanding and reproducibly produce TCO films, the interplay between the microparameters (plasma parameters, not only external parameters) and film quality has to be investigated much more in detail.
P. S. : Partial representative papers:
1. Cebulla R, Wendt R, Ellmer K Al-doped zinc oxide films deposited by simultaneous rf and dc excitation of a magnetron plasma: Relationships between plasma parameters and structural and electrical film properties JOURNAL OF APPLIED PHYSICS 83 (2): 1087-1095 JAN 15 1998 Times Cited: 67
2. Ellmer K Resistivity of polycrystalline zinc oxide films: current status and physical limit JOURNAL OF PHYSICS D-APPLIED PHYSICS 34 (21): 3097-3108 NOV 7 2001 Times Cited: 51
3. Ellmer KMagnetron sputtering of transparent conductive zinc oxide: relation between the sputtering parameters and the electronic properties JOURNAL OF PHYSICS D-APPLIED PHYSICS 33 (4): R17-R32 FEB 21 2000 Times Cited: 51
4. ELLMER K, KUDELLA F, MIENTUS R, et al.INFLUENCE OF DISCHARGE PARAMETERS ON THE LAYER PROPERTIES OF REACTIVE MAGNETRON-SPUTTERED ZNO-AL FILMS THIN SOLID FILMS 247 (1): 15-23 JUL 1 1994 Times Cited: 44
5. Hinze J, Ellmer KIn situ measurement of mechanical stress in polycrystalline zinc-oxide thin films prepared by magnetron sputtering JOURNAL OF APPLIED PHYSICS 88 (5): 2443-2450 SEP 1 2000 Times Cited: 25

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Wednesday, January 24, 2007

Manual for FTG (Film Thickness Module)

I found a free software (FTG, Film Thickness Module) which can be used to determine the thickness of thick films ( usually suitable for the transparent films exceeding 200-300 nm thickness ). Hehe, how about the precision? i don't know :), the details can be refered to the linked paper. Personal viewpoint, the error depending on the value of n, k could be toleranced for the most cased. Fortunately, now the personal manual for FTG has been completed by zmliu which can be reach it at the fellowing address:
http://xbzhangcn.googlepages.com/%E5%AD%98%E6%A1%A3

The Film Thickness Module includes both fringe counting and the FFT technique. It may be downloaded freely and without restrictions from web site
http://www.ftgsoftware.com/
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Friday, January 19, 2007

Congratulation!

Welcome to my blog!
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