My journal highlighted in SciTech

Salam,

Taken from SciTech Asia Pacific website. They highlighted my recently published journal.

Url: http://www.scitechpap.com/?p=661

______________

Monday 25 April 2011

Semiconducting bismuth alloys (MAS, UK)

Malaysian and UK collaboration yields high quality GaAsBi alloys by molecular beam epitaxy for optoelectronic applications.

A precise and reproducible method for controlling the band gap of semiconductors is invaluable for the development of optoelectronic devices. Recent reports show that the addition of bismuth (Bi)—a semimetal—to thin films of gallium arsenide (GaAs) reduces the band gap by 88 meV per percent of Bi. This large reduction in the band gap is promising for the fabrication of long wavelength optical devices.

However, in spite of the tremendous potential of Bi-semiconducting alloys, Bi segregates and forms droplets on GaAs substrates during film deposition.

Here, Abdul Rahman Mohmad at the National University of Malaysia in collaboration with researchers in the United Kingdom describe the photoluminescence (PL) properties of high quality GaAsBi (Bi=3%) thin films grown on GaAs substrates by molecular beam epitaxy.

Notably, the researchers observed a room temperature PL peak at 1038 nm with a full width half maximum of 75 meV, which is significantly narrower than other reports and indicates low alloy fluctuations in the film.

The researchers ascribe the improvement in the film quality to the higher temperature of 400^oC used growth—compared with the typical 270–380^oC.

The ability to produce high quality GaAsBi alloys offers new opportunities for the fabruication optoelectronic devices, including spintronic structures exploiting the the large spin-orbit bowing of GaAsBi alloys.

Further information
Publications and Affiliations
A. R. Mohmad,^1,2 F. Bastiman,¹ J. S. Ng,¹ S. J. Sweeney,³ and J. P. R. David¹, Photoluminescence investigation of high quality GaAs_1−xBi_x on GaAs. Applied Physics Letters, 98, 122107, (2011).

1. Department of Electronic and Electrical Engineering, University of Sheffield, Sir Frederick Mappin Building, Mappin Street, Sheffield S1 3JD, United Kingdom
2. Institute of Microengineering and Nanoelectronics, National University of Malaysia, Bangi, 43000 Selangor, Malaysia
3. Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom

First journal

Salam,

Alhamdulillah thumma Alhamdulillah. Journal pertama saya telahpun di published di Applied Physics Letters (APL) bertajuk "Photoluminescence investigation of high quality GaAsBi on GaAs". Saya telah mula menulis journal ini semenjak July 2010 dan telah melalui 11 proses editting sebelum supervisor saya, Prof. John David dan Dr. Jo Shien Ng berpuas hati untuk submission.

Berikut adalah feedback daripada reviewer;

Reviewer Comments:
Reviewer #1 Evaluations:
RECOMMENDATION: Publish in APL with mandatory revision (minor)
Paper Interesting: Yes
Original Paper: Yes
Sufficient Physics: Yes
Well Organized: Yes
Clear and Error Free: Yes
Conclusions Supported: No
Appropriate Title: Yes
Good Abstract: Yes
Satisfactory English: Yes
Adequate References: Yes
Clear Figures: Yes
OVERALL RATING: Good

Selepas menghantar respond letter dan revise manuscript tersebut, journal tersebut telah diterima untuk publication.

Berikut adalah serba sedikit mengenai APL (Q1).

2009 Journal Citation Data Thomson Reuters*:
The most highly cited journal in Applied Physics (Thomson Reuters, 2009)

Five-Year Impact Factor	3.780
Impact Factor	3.554
Immediacy Index	0.617
Cited Half-Life	5.6
EigenFactor Score	0.71820
Article Influence Score	1.347

*Data from the 2009 Science Edition of Thomson Reuters's Journal Citation Reports ®.

Journal tersebut boleh diaccess menggunakan link di bawah.

Photoluminescence investigation of high quality GaAs_1?xBi_x on GaAs

Appl. Phys. Lett. 98, 122107 (2011)

http://link.aip.org/link/doi/10.1063/1.3565244

Stress dengan Research?

Saya nak share nasihat yang saya peroleh daripada Dr. Firdaus (ex-housemate dan sekarang rakan sekerja di UKM)

biasalah tu, namamya R&D, yg penting you have to keep at it... and enjoy the work, makes life much easier... don't see it as something stressful but something exciting and challenging which makes you get up to go to work every day

if you see it as just a way to get a PhD, memang akan jadi stress

not much of advice, it's just something i observed... some people are there to do a PhD, they get stressed by all the problems associated with research because I think they're not enjoying it enough... jadi satu bebanan... to me, i just saw it as an exciting problem to solve... I actually managed to finish off early and do a postdoc..

Kalau berani buatlah PhD

Semenjak 2 menjak ni, ramai groupmates saya yang tamat dalam PhD mereka. Andrew mengharungi viva nya kira2 2 bulan yang lalu, Fadzlin bulan lepas dan Wai Mun minggu lalu. RA dalam group kami iaitu Lionel pun akan tamat kontraknya pada bulan April tahun depan. Bila melihat mereka yang sudah habis viva ni, terfikir pula macam manalah nasib aku nanti. Selalunya, apa yang terbayang dalam kepala ialah satu perjalanan yang masih jauh. Begitu jauh. Sangat jauh.

Masa mula2 saya buat PhD, ramai orang kata, apa yang kita buat masa first year ni biasanya tak contribute untuk final thesis. Term yang selalu orang guna ialah 'donkey year'. Mula2 saya memang tak percaya atau refuse untuk percaya. Tapi, setelah 8 bulan menjadi PhD student, nampaknya kata2 mereka benar belaka. Walaupun sudah hampir setahun, saya masih lagi tiada results untuk di report.

PhD sangat berbeza dengan Degree and Masters. Untuk degree dan Masters, kita diberi silibus, belajar silibus tersebut dan exam. Project pula adalah straightforward, nothing to lose kind of project dan telah di designed supaya at the end of the project duration, you are guaranteed to get results that you can report. PhD pula sangat berbeza. Dalam PhD, there are elements that you can and can't control, elements of uncertainty and unpredictability, involves a lot of money and you are not guaranteed to get results. In some cases, it also involves internal politics and bureaucracy. That's why sometimes PhD can be so frustrating. Saya teringat kata2 kak Fadzlin dalam email dan blognya,

"Teringat saya kata-kata seorang senior PhD disini masa saya mula2 start buat phD dulu (kak salmiah kasolang kalau sesiapa mengenali beliau)...she said to me 'Fadzlin, every phd candidate has his/her own unique story'... memang benarlah, setiap satu drp kita akan ada perjalanan phd yg unik....ada yg 2 tahun dah siap, ada yg 7 tahun belum siap...ada yg pelbagai ujian dtg menimpa, kalau tidak ujian drp supervisor or academic wise, ada pula cabaran drp keluarga etc....tapi. ..yg pastinya, Allah tidak akan menguji kita lebih drp kemampuan kita masing2...jadi jika ada cabaran mendatang, sudah pasti kita mampu menghadapinya. ..if we persevere, janji Allah pada kita...Innamal 'usri yusra...selepas kesusahan pastinya ada kesenangan.."

Fokus PhD saya agak berbeza berbanding rakan2 dalam group kami (Impact Ionisation Group aka IIG). Ini kerana expertise group kami ialah characterisation of avalanche photodetectors. Namun, untuk PhD saya, saya bukan sahaja involve dengan device characterisations, malah juga akan involve dengan growth and material characterisations.

V90 Molecular Beam Epitaxy

Di Sheffield, ada 2 MBE machines untuk tujuan growth; V80 dan V90. Kedua2 mesin ini sebenarnya milik dan diuruskan oleh National Centre for III-V Semiconductor (NC). Kedua2 mesin ini bukan sahaja supply samples untuk Uni of Sheffield, tetapi untuk Uni2 lain di UK seperti Surrey, Bristol, etc. Aktiviti growth dijalankan oleh 2 orang grower (mempunyai PhD qualification) yang merupakan staff NC. Based on their system, they don't allow students to do growth. Mungkin disebabkan mesin MBE tersebut mahal (the machine plus all the piping cost more than a million pounds), growth involves dealing with highly toxic gaseous (arsine, phosphine) that can cause fatality and not properly trained personnel can easily damage it.

V80 MBE

V80 MBE

Disebabkan perkara2 yang dinyatakan diatas, arrangement untuk membolehkan saya di trained sahaja telah mengambil masa berbulan lamanya. Mungkin position John sebagai Head of Department sedikit sebanyak telah mempercepat proses tersebut. Kini, growth training saya telahpun bermula. Intensive training tersebut sahaja dijangka akan mengambil masa 6-9 bulan. (Ini bermakna saya tidak akan mempunyai sample sendiri serta results dalam 6-9 bulan akan datang. Nampaknya terpaksalah den transfer bila dah 2 tahun. huhu).

Mudah2an training tersebut akan berjalan lancar. Di Malaysia hampir tiada grower. Hopefully, I can become an expert in growth and contribute my expertise.

Ipswich dan Ba Alif Ba Ya

Khamis yang lalu, saya telah pergi ke Ipswich untuk menghadiri ETOE 2 (Extended Temperature Optoelectronics) project meeting. Projek ini melibatkan Uni of Sheffield, Uni of Surrey, Loughborough Surface Analysis (LSA), CIP Technologies, Oclaro (formerly known as Bookham) dan SAFC Hitech. Aim utama projek ini ialah untuk menghasilkan 1.55-1.6um dilute nitride lasers on GaAs and InP substrate. Role Sheffield ialah MBE growth dan fabrication.

Saya pergi bersama Research Associate group kami iaitu Dr. Lionel Tan dengan menaiki kereta. Kami bertolak seawal 6.30am dan perjalanan pergi mengambil masa kira-kira 4 jam.

2 jam pertama di dedicate untuk technical meeting manakala 2 jam seterusnya untuk administration meeting. Environment meeting agak relaks. Setiap companies present progress masing2 untuk 3 bulan yang lepas. Isi kandungan presentation mereka adalah CONFIDENTIAL.

Meeting tersebut tamat kira2 jam 3 petang dan kami sampai ke Sheffield pada pukul 7.15pm. Selepas itu, saya terus ke masjid IC untuk hadiri iftar. Ingatkan tak sempat nak join iftar, tapi Alhamdulillah, sampai Sheffield awal.

Semasa on the way ke Ipswich, saya nampak something interesting. Dah lama saya cari tempat ni, tapi tak jumpa2. Sebenarnya, tempat yang saya maksudkan ialah pig farm. haha. Itulah kali pertama saya nampak pig farm di UK. Pig farm tu terletak di tepi highway kira2 40 min dari Ipswich. Seperti sedia maklum, di Msia, khususnya Melaka dan Selangor pernah kecoh pasal pig farm ni. Melaka dok sibuk nak tutup pig farm dan Selangor pulak sibuk nak bukak pig farm yang kononnya berteknologi tinggi. Sekarang ni tak tahulah apa status pig farm berteknologi tinggi kt S'gor tu.

Isu utama yang sering berkait rapat dgn pig farm ialah isu kebersihan, bau etc..... Saya pernah berborak dgn kawan2 pasal isu ni. Saya kata, 'selama kat UK ni, tak pernah pulak aku dengar pasal isu babi ni. Padahal sepatutnya kat sini ada lagi banyak babi'. Kawan saya pun jawab, 'kat UK pun mesti ada isu ni. Tapi mungkin isu babi ni dah diorang alami 20 tahun lepas. Sebab tu la sekarang ni tak ada isu pasal pig farm'.

Sebab itulah saya beria2 nak tengok berapa canggih pig farm kt UK ni sampai tak timbul isu kebersihan etc.

Daripada observations saya, cara mereka bela babi di sini lebih kurang saja dengan cara mereka bela kambing. Babi2 tersebut dibiar bebas di atas padang. Tapi setiap lebih kurang 5 meter, ada dibina shelter2 untuk babi2 tersebut. Sekali pandang, saya tak nampak pun apa yang boleh dikatakan teknologi tinggi. Babi2 tu mestilah berak dan kencing kat padang tu juga. Tapi tak tahulah kalau kt bawah tanah, ada special piping supaya air kencing babi tu boleh dialirkan secara sistematik. haha.

Daripada apa yang saya lihat, babi2 di msia pula sentiasa dikurung dalam kandang. Itulah tempat dia makan, itulah tempat dia berak, kencing, mengawan dll. Manalah diorg tak stress. hehe.

PS; babi meragut rumput macam kambing jugak ke?

Photodetectors vs Solar Cells

Kini, PhD saya sudah 4 bulan berlalu. Kalau mengikut proposal mula-mula, saya akan buat dilute nitride Avalanche photodetector. Namun, bila saya diletakkan bawah projek dilute nitride lasers, saya ingat, saya akan buat lasers. Jadi, saya pun bacalah banyak pasal lasers. Rupa2nya, saya tetap buat detector untuk PhD saya, cuma dalam masa yang sama terlibat dengan projek laser juga.

Terlibat dengan 2 projek dalam satu masa ni ada baik dan buruknya. Baiknya, kita dapat lebih banyak jurnal dan conference papers walaupun kita bukan first author. Rakan2 satu group saya yang terlibat dengan beberapa projek semasa buat PhD berjaya grad dengan lebih kurang 15 jurnal dan conference papers. Buruknya pula, masa kita sudah terbahagi antara projek PhD kita dan projek2 lain. Sebab itulah mereka yang terlibat dalam banyak projek ambil masa yang lama untuk habis PhD.

Sebenarnya dalam group saya, sudah ada 4 orang yang buat research mengenai dilute nitride detector. Disebabkan ramai yang buat research theme yang sama, supervisor bahagi2kan topik supaya masing2 tidak buat perkara yang sama atau bertindih (walaupun boleh buat topik yang sama tapi kaji dari aspek yang berbeza). Secara tradisinya, pelajar yang lebih lama ada kebebasan untuk pilih topik mana yang mereka nak buat.

Jadi, selepas berbincang dengan supervisor, dia akhirnya suruh saya buat dilute nitride solar cells. Dilute nitride ini memang material yang useful. Material ini boleh digunakan sebagai lasers, photodetector, solar cells, modulator dll. Basic untuk detector dan solar cells ni lebih kurang, kerana kedua2 peranti tersebut convert light to current. Cuma parameter yang perlu dioptimise berbeza.

Solar cells merupakan bidang baru kepada group saya. Maka, kami tiada previous knowledge serta kelengkapan khusus untuk characterise solar cells. Contohnya, solar simulator. Research PhD saya nanti akan berkisar kepada growth dan characterisation. Persoalan yang perlu dijawab ialah apakah growth condition yang optimum untuk growth high quality dilute nitride? Dilute nitride ni memang terkenal dengan sifatnya yang banyak defects. Bila kita ubah satu growth parameter, adakah defects semakin berkurang, sama atau semakin teruk? Satu masalah untuk menghasilkan efficient solar cells, pin diodes dll ialah unintentional doping di intrinsic region. Perkara tersebut merupakan key untuk hasilkan high performance devices.

Saya mungkin tidak akan menghasilkan full structure multijunction solar cells tersebut. Ini kerana untuk menghasilkan multijunction solar cells, kita perlu studi lagi 3 jenis material iaitu InGaP, GaAs dan Ge. Mungkin supervisor saya akan ambil lagi PhD student untuk kaji material tersebut. Tetapi research ini amat penting dan akhirnya akan menjurus kepada penghasilan high efficiency multijunction solar cells pada masa akan datang.

Ada baiknya juga saya terlibat banyak dalam growth untuk PhD saya. Ini kerana di Malaysia, grower yang pakar hampir tiada. Jadi, kepakaran dalam bidang ini amatlah diperlukan. Sekiranya kita ada grower yang pakar, secara tidak langsung research berkaitan III-V material di Malaysia akan berkembang. Ini kerana sekarang kita hanya banyak buat simulation sahaja. Kalau hendak grow, kita hantar design/recipe ke grower luar.

Di sheffield, kita ada 2 MBE machine untuk aktiviti growth. Satu V80 (model lama) dan satu V90 (model baru). Supervisor saya nak saya belajar growth guna V80, pasal V90 ada banyak automated features. Analogi yang mudah ialah beza kereta manual dan auto. Seseorang yang tahu bawak kereta manual mudah untuk bawak kereta auto, tapi orang yang tahu bawak kereta auto belum tentu boleh bawak kereta manual. Tapi, masalahnya, grower V80 sedang bercuti panjang kira2 sebulan lebih kerana isteri bersalin. Jadi, saya hanya boleh belajar growth selepas dia balik daripada bercuti. sigh!!!

Dilute Nitride: What and Why

For decades, InP (indium phosphide) based lasers have dominated the optical communication market especially for long haul. This is because it was believed that there was no other material lattice matched to GaAs (gallium arsenide) that can emit > 1.1 micron. However, InP is very expensive. As a result, the cost to setup a modern MAN or LAN is simply too high because it requires tens of millions of lasers.

Around 1995, Kondow et al have proposed a new material called GaInNAs (gallium indium nitride arsenide) which capable of emitting light at 1.3 micron. This material is also called dilute nitride because a very low percent of Nitrogen is incorporated in the material. Because this new material can be grown on GaAs substrate which is considerably cheaper than InP (InP substrate cost 3x) and has greater conduction band offset which lead to better carrier confinement hence, can operate at higher temperature, dilute nitride has become a centre of attention among researchers in the world.

Besides, the established GaAs/AlAs mirror for DBR also can be incorporated with dilute nitride to design a VCSEL because the material is lattice matched to GaAs. High power pump lasers for Raman amplifier also can be further developed due to greater conduction band offset of dilute nitride.

However, there are lots of challenges that need to be tackled before dilute nitride based devices can penetrate the market. The incorporation of Nitrogen has significantly degrade the quality of the material. Therefore, high percentage of N cannot be incorporated to push the wavelength up to 1.55 micron. It was reported that Sb (antimony) can be used to keep the material grow in 2D and allows for higher N incorporation. However, the role of Sb and how it affects the bandgap is still unknown.

Besides, the usage of different material for the quantum well barrier also has proven to help reducing the bandgap. Material such as GaNAs or GaInNAs with different composition can be used instead of GaAs barrier.

Based on current research, dilute nitride based devices are far from being optimised. This is because this technology is largely material and knowledge limited. New knowledge on growth, material fundamentals and defect in arsenide-nitride are essential to bring this technology forward.

Journal Analysis: Where to publish?

Choosing the right journal to publish our papers is very important. There are four aspects that we should consider; Total citations, number of articles published, trend line (citations divided by number of articles published) and % not cited.

In this entry, I will compare 4 journals that i frequently use which are Applied Physics Letters, Journal of Applied Physics, Journal of Crystal Growth and Physical Review Letters.

Physical Review Letters has superior # of citations and ratio between citations and # of articles published (trend line).

Even though Journal of Crystal Growth has the lowest # of citations and publications but it has the lowest % of not cited (which is good!).

Applied Physics Letters has the highest # of publications from 2005 onwards but the # of citations and trend line did not increase. Quality increase?

The % of not cited for all journals increased rapidly from 2005 to nearly 100% in 2008. Is that means new papers are not quality? No, don't get it wrong. The % of not cited was high because the papers were just published. The # of citations for new papers will increase over time. So % of not cited will reduce and probably down to less than 10% like the old papers in a few years time.

Methods to Evaluate an Author

Traditionally, the sole method to measure the performance of a researcher/author is based on the number of publications. More publication means better performance. In fact, most universities require their researchers and academic staff to publish a minimum number of publications every year. i.e 4 international journal papers a year. However, this method of assessment may lead to a situation called the ‘salami publishing’. This kind of situation happened when an author tend to publish materials which suppose to be reported in one paper to several papers simply to increase the number of publications. As a result, the published papers will be full of old materials and just a minute percent of new knowledge.

Then, people start to consider the total/average citations per paper. The number of citations indicates the number of people who refer to a paper and eventually its quality. But, question arose. Which one is a better author; the one who produce one paper with 200 citations and zero for others (one-hit wonders) or an author who publish several papers but each paper has 20 citations? Besides, total/average number of citations per paper may penalize productivity.

Later, journals were evaluated periodically and given the impact factor. Generally speaking, only high quality research papers can be published in high impact factor journals. The higher the impact factor, the harder to publish in it. So, where authors publish their papers is also used to evaluate them. However, impact factor which can vary from less than one to above one hundred also vary depending on research areas. A science journal may have impact factor of 100 while journal for social sciences have impact factor of 0.1. So, it seemed unfair to compare authors from different background by using impact factor.

In 2005, a new method of evaluating authors called ‘h-index’ was proposed by Jorge Hirsh, a condensed-matter physicist and peace activist at University of California in San Diego. h-index combines quantity, quality, productivity and influence to evaluate authors. It is easy to determine and dynamic which means it can change as citations and publications increase. Besides, it ignores the highly and poorly cited papers (one-hit wonders) and age of author is also not taken into account. This means both junior and senior authors can have high or low h-index. Based on this method, a researcher has index h if h of his papers have at least h citations each and the other papers have no more than h citations each.

Besides, h-index also can be used to measure the performance of institutions, universities, departments, faculties, journals etc. The h-index method is not perfect but so far, it is the most balance method of evaluation.

I have used SCOPUS to look at the performance of Prof. Joe C Campbell, who is generally accepted as the guru or world leader in the field of avalanche photodiodes research. Click on the pictures to enlarge.

Prof. Campbell has published 453 papers, his papers were cited by 2688 people and has h-index of 29 (very large h-index)

The highest number of papers were published in 2002; 37 papers

Distribution of citations

Don't be shocked if you find out that a professor in small/new university has zero h-index and 2 or 3 citations only. Publications produced by a professor in top university in a year also may be more than the number of publications produced by a small UNIVERSITY.

Curious to see how your supervisor perform?