Leroy L. Chang (; 20 January 1936 – 10 August 2008) was an experimental physicist and

solid state electronics Solid-state electronics means semiconductor electronics: electronic equipment using semiconductor devices such as transistors, diodes and integrated circuits (ICs). The term is also used as an adjective for devices in which semiconductor electr ...

researcher and engineer. Born in China, he studied in

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

and then the United States, obtaining his doctorate from Stanford University in 1963. As a research physicist he studied

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

s for nearly 30 years at IBM's

Thomas J. Watson Research Center The Thomas J. Watson Research Center is the headquarters for IBM Research. The center comprises three sites, with its main laboratory in Yorktown Heights, New York, U.S., 38 miles (61 km) north of New York City, Albany, New York and wit ...

, New York. This period included pioneering work on

superlattice A superlattice is a periodic structure of layers of two (or more) materials. Typically, the thickness of one layer is several nanometers. It can also refer to a lower-dimensional structure such as an array of quantum dots or quantum wells. Disc ...

heterostructure A heterojunction is an interface between two layers or regions of dissimilar semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. It is often advantageous to engineer the electronic energy bands in m ...

s with Nobel Prize-winning physicist

Leo Esaki Reona Esaki (江崎玲於奈 ''Esaki Reona'', born March 12, 1925), also known as Leo Esaki, is a Japanese physicist who shared the Nobel Prize in Physics in 1973 with Ivar Giaever and Brian David Josephson for his work in electron tunneling i ...

. In 1993, Chang moved from New York to Hong Kong, switching from industrial research into academia in anticipation of the 1997 transfer of the British colony to China. He was among the first wave of recruits to the

Hong Kong University of Science and Technology The Hong Kong University of Science and Technology (HKUST) is a public research university in Clear Water Bay Peninsula, New Territories, Hong Kong. Founded in 1991 by the British Hong Kong Government, it was the territory's third institut ...

. Over the following 14 years he helped build the university's reputation in his roles as Dean of Science, Professor of Physics, Vice-President for Academic Affairs, and Emeritus Professor. He retired in 2001. Honours bestowed on Chang included membership of the US National Academy of Sciences, the

Chinese Academy of Sciences The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Republi ...

, and Academia Sinica, the national academy of Taiwan. Awards received included the

International Prize for New Materials The James C. McGroddy Prize for New Materials is a prize that has been awarded annually by the American Physical Society since 1975, but was only given that name following its endowment by IBM in 1999. Prior to that it was known as the Internation ...

(1985), the David Sarnoff Award (1990) and the

Stuart Ballantine Medal {{notability, date=February 2018 The Stuart Ballantine Medal was a science and engineering award presented by the Franklin Institute, of Philadelphia, Pennsylvania, USA. It was named after the US inventor Stuart Ballantine. Laureates *1947 - Geo ...

(1993). Chang's death in 2008 was marked with memorial services, and a symposium in his memory was held the following year.

Early life and education

Leroy L. Chang's family was from Jiutai County,

Jilin Jilin (; alternately romanized as Kirin or Chilin) is one of the three provinces of Northeast China. Its capital and largest city is Changchun. Jilin borders North Korea ( Rasŏn, North Hamgyong, Ryanggang and Chagang) and Russia (Prim ...

province in

Northeastern China Northeast China or Northeastern China () is a geographical region of China, which is often referred to as "Manchuria" or "Inner Manchuria" by surrounding countries and the West. It usually corresponds specifically to the three provinces east of ...

(Manchuria). After Manchuria was occupied by

Imperial Japan The also known as the Japanese Empire or Imperial Japan, was a historical nation-state and great power that existed from the Meiji Restoration in 1868 until the enactment of the post-World War II 1947 constitution and subsequent forma ...

in 1931, his family escaped to inland China and Chang was born on 20 January 1936 in

Kaifeng Kaifeng () is a prefecture-level city in east-central Henan province, China. It is one of the Eight Ancient Capitals of China, having been the capital eight times in history, and is best known for having been the Chinese capital during the No ...

Henan Henan (; or ; ; alternatively Honan) is a landlocked province of China, in the central part of the country. Henan is often referred to as Zhongyuan or Zhongzhou (), which literally means "central plain" or "midland", although the name is al ...

province. His father was , a well-known geologist and Republic of China official who was assassinated by the

Communists Communism (from Latin la, communis, lit=common, universal, label=none) is a far-left sociopolitical, philosophical, and economic ideology and current within the socialist movement whose goal is the establishment of a communist society, a s ...

in 1946. His mother, Li Xiangheng,Leslie T. Chang (2010
''Factory Girls: Voices from the Heart of Modern China''
p95 was one of the first group of women elected to the Legislative Yuan in 1948. After moving to

, Chang studied electrical engineering at

National Taiwan University National Taiwan University (NTU; ) is a public research university in Taipei, Taiwan. The university was founded in 1928 during Japanese rule as the seventh of the Imperial Universities. It was named Taihoku Imperial University and served d ...

, graduating in 1957. He obtained his master's degree in 1961 at the University of South Carolina. His doctorate (PhD) in

solid-state electronics Solid-state electronics means semiconductor electronics: electronic equipment using semiconductor devices such as transistors, diodes and integrated circuits (ICs). The term is also used as an adjective for devices in which semiconductor electr ...

and electrical engineering was awarded by Stanford University in 1963.

Industry, research and academia

Between 1963 and 1992, with the exception of a sabbatical year, Chang worked at IBM's

, New York, USA. He held the position of researcher for some 12 years (1963 to 1968; 1969 to 1975), with a sabbatical year as Associate Professor at the Department of Electrical Engineering at the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

(1968-9). On his return to IBM research, he spent 9 years as manager of its

Molecular Beam Epitaxy Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors, and it is considered one of the fundamental tools for the devel ...

section (1975 to 1984). This was followed by 7 years as manager of the Quantum Structure section (1985 to 1992). His research included

semiconductor physics A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

, low-dimensional electron systems, and

nanostructures A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale. In describing nanostructures, it is necessary to differentiate between the number of dime ...

. In the 1970s, he pioneered development of

quantum well A quantum well is a potential well with only discrete energy values. The classic model used to demonstrate a quantum well is to confine particles, which were initially free to move in three dimensions, to two dimensions, by forcing them to occupy ...

and superlattice structure (SLS) techniques. One of the key results from Chang's work in this period was using

molecular beam epitaxy Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors, and it is considered one of the fundamental tools for the devel ...

to grow

structures in

s. This research was described in a 1973 paper in '' Journal of Vacuum Science and Technology'' that was cited multiple times over the following years. Eleven years later, in 1984, this pioneering research paper was featured as a Citation Classic by ISI, an organisation that tracks and measures

impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, as ...

and citation frequency and volume for journals and individual research papers. Commentary for this retrospective article was provided by Chang. The impact of the research carried out in the 1970s by Chang and his colleagues, including Nobel Prize-winning

and Ray Tsu, was highlighted by IBM researchers Theis and Coufal in 2004:

Leo Esaki, Ray Tsu, and Leroy Chang began to envision and investigate designed quantum structures — which are based on interfaces between lattice-matched compound semiconductors — early in the 1970s. Ever since, the study of electronic systems of minute dimensions has ranked among the most exciting areas of condensed-matter physics.

After 29 years at IBM, Chang moved from industrial research into academia, being appointed the first Dean of Science at

(HKUST) in 1993. This was a new university, having been established in 1991. Chang's arrival was described in a 2011 account of the rise of this university: "Other recruits during the first decade included Leroy Chang, a world-renowned experimental physicist from International Business Machines (IBM)". Chang held the position of Dean of Science until 1998, when he became Vice President of Academic Affairs until stepping down from this role in 2000. During and after this period, from 1997 until his retirement in 2001, he was also Professor of Physics and Electrical and Electronic Engineering at the university. Chang's departure from New York and arrival in Hong Kong in 1993 was part of a wider influx that saw many leading scientists and researchers taking up positions at universities and institutions in the British colony to be able to advantage of the opportunities presented by the 1997 transfer to Chinese control. Quoted in an article in 1996, Chang stated:

I would never have come to Hong Kong if it was going to remain just a British colony. We came because of 1997.

In addition to his work at HKUST, Chang also supported other science and technology institutions in Hong Kong and the wider region. From 1996 to 1998, he was President of the Hong Kong Institute of Science. In 1998, Chang played a key role in the founding and establishment of the Research Center for Applied Sciences (RCAS) of the Academia Sinica in Taiwan, serving on its advisory committee. He was Emeritus Professor at the Hong Kong University of Science and Technology from his retirement on 15 March 2001 until his death.

Awards and honours

*1984: Fellow of the American Physical Society *1985: American Physical Society's

(shared with

and Raphael Tsu): "For his conception of artificial semiconductor superlattices and his recognition that such structures have realizable and ... novel electronic properties. His sustained experimental and theoretical efforts have helped lead the way to versatile new materials and technologies." *1988: Member of the

National Academy of Engineering The National Academy of Engineering (NAE) is an American nonprofit, non-governmental organization. The National Academy of Engineering is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of ...

: "For pioneering achievements in superlattice heterostructures." *1990: Fellow of the Institute of Electrical and Electronics Engineers: "For contributions to superlattices and semiconductor quantum wells." *1990: IEEE's David Sarnoff Award: "For pioneering contributions to the realization and development of quantum wells and superlattices." *1993:

Franklin Institute The Franklin Institute is a science museum and the center of science education and research in Philadelphia, Pennsylvania. It is named after the American scientist and statesman Benjamin Franklin. It houses the Benjamin Franklin National Memori ...

(Physics) *1994: Member of the United States National Academy of Sciences *1994: Foreign Member of the

(one of the first 14 foreign members, elected 8 June 1994) *1994: Academician of Academia Sinica (Taiwan) *1994: Member of the

Hong Kong Academy of Engineering Sciences The Hong Kong Academy of Engineering Sciences (HKAES) is an engineering science institution based in Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. H ...

*1995: Honorary Doctor of Science (D.Sc.) from HKUST

Death and tributes

Chang died on 10 August 2008 in California, USA. Memorial services were held in the El Camino Memorial Park, San Diego, USA, and at the Hong Kong University of Science and Technology. A memorial symposium in his honour, 'Recent Advances in Applied Sciences', was held in 2009 at the Academia Sinica. The symposium program included "A Tribute to Academician Leroy Chang" and "Remembering Leroy: from SL/QW to RCAS". At the time of his death, tributes were paid to Chang by his HKUST colleagues, including the university's founding president Chia-Wei Woo:

Leroy was always exuberant and high-spirited, logical and sensible, forceful and clear, efficient and effective – and always full of wit and humor. As Dean of Science and Vice-President for Academic Affairs, he gave up his beloved and world-renowned scientific career to work totally selflessly towards providing a sound academic environment for his colleagues. HKUST's founding members could not have had a stronger comrade-in-arms in building this new university. I so very deeply mourn his passing.

Personal life

Chang's daughter Leslie T. Chang is an author and journalist who is married to

Peter Hessler Peter Benjamin Hessler (born June 14, 1969) is an American writer and journalist. He is the author of four books about China and has contributed numerous articles to ''The New Yorker'' and ''National Geographic'', among other publications. In 201 ...

, author of several books about China.

Early life and education

Industry, research and academia

Awards and honours

Death and tributes

Personal life

References

External links