Lau Wai Shing
Encyclopedia
Wai Shing Lau is also known as Lau Wai Shing. Lau is an electrical engineer and also materials scientist. He worked on both Si-based and III-V based microelectronics.
He graduated in Electrical Engineering at the University of Hong Kong in 1977. He obtained a master's degree from the Department of Electronics, the Chinese University of Hong Kong
in 1980. Subsequently, he published a paper on the analysis of constant-capacitance deep-level transient spectroscopy by negative feedback
theory in 1982. For his PhD in Electrical Engineering from the Pennsylvania State University, Pennsylvania, USA in 1987 he worked on transparent conductive thin films like tin oxide
, indium oxide and zinc oxide
. Then he served as a post-doctoral student in the same laboratory to work on PECVD silicon nitride
samples from IBM
. New insight was gained regarding hysteresis
in the C-V characteristics and how to suppress it in MNS (metal-nitride-silicon) capacitors.(Please see references [1]-[3].)
Lau served as lecturer and then senior lecturer in the National University of Singapore
from 1988 to 1997.
Lau worked on gallium arsenide and gallium nitride devices and materials. He developed the "true oxide electron beam induced current
" (TOEBIC) technique to study local defects in insulating thin films. TOEBIC can be applied to MOS capacitors. Dr. Lau's theory was that local defects in the oxide and local defects in silicon could be distinguished when electron beam induced current
was performed on M/SiO2/Si capacitor structures. (Please see references [4]-[6].) He proposed to use PECVD silicon nitride
/ polyimide
dual passivation for AlGaN/GaN HEMT
(high electron mobility transistor). When PECVD silicon nitride is thick, there is mechanical stress problem. It may also have pinholes. Polyimide
can be quite thick without stress problem but it is not a good barrier for moisture. Thick polyimide
can cover up the pinholes in the PECVD silicon nitride
below. The two combined together with polyimide
on top of the nitride can be a practical and better approach. In addition, the dielectric constant
of polyimide
(about 3.5) is smaller than that of PECVD silicon nitride
(about 7), resulting in less parasitic capacitance. (Please see references [7].)
Dr. Lau also worked on Ohmic contact
technology for GaN and AlGaN/GaN HEMT
. He noticed that the presence of a small quantity of moisture in the rapid thermal annealing chamber is particularly bad for Ohmic contact
on AlGaN/GaN HEMT
wafers. However, this is less serious for Ohmic contact
on GaN only. (Please see references [8].)
Dr. Lau has also published a paper on low frequency noise in polysilicon emitter bipolar transistors in 1992. Basically, the application of a very thin layer of interfacial oxide between the polysilicon emitter and the single-crystalline emitter can help to increase the current gain. However, this approach will very significantly increase low frequency noise probably because of tunneling 1/f noise.
During 1997-1998, he worked on embedded DRAM
technology in Chartered Semiconductor Manufacturing
, Singapore
. He studied the mechanism of under-sensitive test structures and over-sensitive test structures. He pointed out that if this is properly understood, electrical failure analysis
can be more easily achieved by electrical testing at the test structure level instead of at the product engineering level. This will make the job of DRAM yield enhancement easier.
Dr. Lau became an associate professor in the Nanyang Technological University
since 2001.
He was the first in making a correlation between the leakage current of ultrathin tantalum pentoxide (one of the high-k dielectric) films with defect states detected by zero-bias thermally stimulated current
. Most scientists cannot see any relationship between the leakage current in tantalum oxide (tantalum pentoxide) and the defect states detected by thermally stimulated current. For example, Dr. Yasushiro Nishioka (Japan) could not see any relationship between the leakage current and the defect states detected by thermally stimulated current (private communication). Dr. Lau managed to see the relationship between the leakage current and the defect states and published his theory in various papers. He invented "zero temperature gradient zero bias thermally stimulated current
" as a method to detect defect states in ultrathin high-k dielectric films. This was patented as US Patent 6909273 in 2005. (Please also see reference [9].) In addition, he has also developed a technique known as "two-scan zero-bias thermally stimulated current
" when an insulator or semiconductor has some traps which can be filled at low temperature and some traps which can only be filled at relatively high temperature. (Please see reference [10].)
He also worked on Cu/low-k
back-end-of-line (BEOL) technology. (Please see reference [11].)
He also wrote various papers on MOS transistors. For example, he worked on the application of strain engineering
to CMOS
technology. He pointed out that if tensile stress can increase the on current of n-channel MOS transistors, tensile stress will also increase the off current. Then he proposed a theory why tensile stress can improve n-channel MOS transistors even though there is an increase in the off current. A lady graduate student, Peizhen Yang, was recruited to work on research in this direction. (Please see references [12] & [13].) Similarly, his theory can be applied to the study of p-channel MOS transistors with the conventional <110> channel or the newer <100> channel. (Please see reference [14].) He also studied the reduction of boron lateral channelling (physics)
due to switching from the conventional <110> channel to the newer <100> channel.
Dr. Lau also studied the theory of electron mobility
in Si-based MOSFET
. In 2005, Dr. Lau pointed out as Lau's hypothesis that "remote Coulombic scattering" is only important in the subthreshold region and in the region slightly above threshold. (Please see reference [15].)
Dr. Lau also explained the observation of anomalous narrow channel effect in very short p-channel MOSFET
. This effect is relatively weak in n-channel MOSFET
. An explanation why this effect is strong in PMOS but weak in NMOS has been proposed by Dr. Lau; p-type dopants like boron tends to segregate into the STI oxide while n-type dopants tend to accumulate at the STI oxide/Si interface. (Please see references [16] & [17].)
Dr. Lau is also interested in quasi-ballistic transport
in MOS transistors and has published his theory on it. (Please see reference [18].) Instead of a carrier saturation velocity according to convention velocity saturation
theory, an effective saturation velocity can be defined. It turns out that the value of effective saturation velocity in real-life MOS transistors is similar to established values of the carrier saturation velocity. However, Dr. Lau pointed out that the effective saturation velocity can be a function of the gate voltage.
Besides semiconductor materials and devices research, Dr. Lau also works privately on the research of traditional Chinese medicine
, foot or hand reflexology
, "unrefreshing sleep", chronic fatigue syndrome
, irritable bowel syndrome
, toothache
, etc. For example, he noticed that there are two toothache
mechanisms according to his personal experience: (A) Mechanism according to Western medicine and (B) Mechanism according to traditional Chinese medicine
. He had direct experience of toothache
which can be easily explained by Western medicine and also a kind of toothache
which cannot be explained by Western dental theory but can be explained by traditional Chinese medicine
. Thus the two mechanisms are not contradictory. They are actually complementary. The solution of the second kind of toothache
is explained in various books on traditional Chinese medicine
. However, those solutions are too complicated or inconvenient for an ordinary person living in the Western World; Dr. Lau has privately developed a much simpler and convenient solution (unpublished). Dr. Lau is also interested in the application of Oldenlandia diffusa (a Chinese herb) to treat some medical problems.
He has also worked on the application of infrared spectroscopy
to semiconductor materials. He has published a book "Infrared Characterization for Microelectronics", World Scientific
, Singapore, 1999. He has also developed some new insight regarding the application of Raman spectroscopy
to health problems. He has also done some work on control theory
and applied it to his research. The application of negative feedback
control to a chaotic system is highly challenging. He has developed some insight on the practical feedback control of chaotic systems.
Biography
Lau was born in Hong Kong in 1955 to Lau Pak Chau (1922–2008), a public health inspector and amateur painter, and Tse Kwan Fong (1931–1988). He has 2 older brothers and 2 younger sisters.He graduated in Electrical Engineering at the University of Hong Kong in 1977. He obtained a master's degree from the Department of Electronics, the Chinese University of Hong Kong
Chinese University of Hong Kong
The Chinese University of Hong Kong is a research-led university in Hong Kong.CUHK is the only tertiary education institution in Hong Kong with Nobel Prize winners on its faculty, including Chen Ning Yang, James Mirrlees, Robert Alexander Mundell and Charles K. Kao...
in 1980. Subsequently, he published a paper on the analysis of constant-capacitance deep-level transient spectroscopy by negative feedback
Negative feedback
Negative feedback occurs when the output of a system acts to oppose changes to the input of the system, with the result that the changes are attenuated. If the overall feedback of the system is negative, then the system will tend to be stable.- Overview :...
theory in 1982. For his PhD in Electrical Engineering from the Pennsylvania State University, Pennsylvania, USA in 1987 he worked on transparent conductive thin films like tin oxide
Tin oxide
Tin oxide may refer to:* Tin oxide , SnO* Tin dioxide , SnO2...
, indium oxide and zinc oxide
Zinc oxide
Zinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...
. Then he served as a post-doctoral student in the same laboratory to work on PECVD silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
samples from IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
. New insight was gained regarding hysteresis
Hysteresis
Hysteresis is the dependence of a system not just on its current environment but also on its past. This dependence arises because the system can be in more than one internal state. To predict its future evolution, either its internal state or its history must be known. If a given input alternately...
in the C-V characteristics and how to suppress it in MNS (metal-nitride-silicon) capacitors.(Please see references [1]-[3].)
Lau served as lecturer and then senior lecturer in the National University of Singapore
National University of Singapore
The National University of Singapore is Singapore's oldest university. It is the largest university in the country in terms of student enrollment and curriculum offered....
from 1988 to 1997.
Lau worked on gallium arsenide and gallium nitride devices and materials. He developed the "true oxide electron beam induced current
Electron beam induced current
Electron beam induced current is a semiconductor analysis technique performed in a scanning electron microscope or scanning transmission electron microscope . It is used to identify buried junctions or defects in semiconductors, or to examine minority carrier properties...
" (TOEBIC) technique to study local defects in insulating thin films. TOEBIC can be applied to MOS capacitors. Dr. Lau's theory was that local defects in the oxide and local defects in silicon could be distinguished when electron beam induced current
Electron beam induced current
Electron beam induced current is a semiconductor analysis technique performed in a scanning electron microscope or scanning transmission electron microscope . It is used to identify buried junctions or defects in semiconductors, or to examine minority carrier properties...
was performed on M/SiO2/Si capacitor structures. (Please see references [4]-[6].) He proposed to use PECVD silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
/ polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...
dual passivation for AlGaN/GaN HEMT
HEMT
High electron mobility transistor , also known as heterostructure FET or modulation-doped FET , is a field effect transistor incorporating a junction between two materials with different band gaps as the channel instead of a doped region, as is generally the case for MOSFET...
(high electron mobility transistor). When PECVD silicon nitride is thick, there is mechanical stress problem. It may also have pinholes. Polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...
can be quite thick without stress problem but it is not a good barrier for moisture. Thick polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...
can cover up the pinholes in the PECVD silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
below. The two combined together with polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...
on top of the nitride can be a practical and better approach. In addition, the dielectric constant
Dielectric constant
The relative permittivity of a material under given conditions reflects the extent to which it concentrates electrostatic lines of flux. In technical terms, it is the ratio of the amount of electrical energy stored in a material by an applied voltage, relative to that stored in a vacuum...
of polyimide
Polyimide
Polyimide is a polymer of imide monomers. The structure of imide is as shown. Polyimides have been in mass production since 1955...
(about 3.5) is smaller than that of PECVD silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
(about 7), resulting in less parasitic capacitance. (Please see references [7].)
Dr. Lau also worked on Ohmic contact
Ohmic contact
An ohmic contact is a region on a semiconductor device that has been prepared so that the current-voltage curve of the device is linear and symmetric. If the I-V characteristic is non-linear and asymmetric, the contact is not ohmic, but is a blocking or Schottky contact...
technology for GaN and AlGaN/GaN HEMT
HEMT
High electron mobility transistor , also known as heterostructure FET or modulation-doped FET , is a field effect transistor incorporating a junction between two materials with different band gaps as the channel instead of a doped region, as is generally the case for MOSFET...
. He noticed that the presence of a small quantity of moisture in the rapid thermal annealing chamber is particularly bad for Ohmic contact
Ohmic contact
An ohmic contact is a region on a semiconductor device that has been prepared so that the current-voltage curve of the device is linear and symmetric. If the I-V characteristic is non-linear and asymmetric, the contact is not ohmic, but is a blocking or Schottky contact...
on AlGaN/GaN HEMT
HEMT
High electron mobility transistor , also known as heterostructure FET or modulation-doped FET , is a field effect transistor incorporating a junction between two materials with different band gaps as the channel instead of a doped region, as is generally the case for MOSFET...
wafers. However, this is less serious for Ohmic contact
Ohmic contact
An ohmic contact is a region on a semiconductor device that has been prepared so that the current-voltage curve of the device is linear and symmetric. If the I-V characteristic is non-linear and asymmetric, the contact is not ohmic, but is a blocking or Schottky contact...
on GaN only. (Please see references [8].)
Dr. Lau has also published a paper on low frequency noise in polysilicon emitter bipolar transistors in 1992. Basically, the application of a very thin layer of interfacial oxide between the polysilicon emitter and the single-crystalline emitter can help to increase the current gain. However, this approach will very significantly increase low frequency noise probably because of tunneling 1/f noise.
During 1997-1998, he worked on embedded DRAM
Dram
Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...
technology in Chartered Semiconductor Manufacturing
Chartered Semiconductor Manufacturing
Prior to 2010, Chartered Semiconductor Manufacturing was the world's third largest dedicated independent semiconductor foundry, with its headquarters and main operations located in the Woodlands Industrial Park, Kranji Singapore...
, Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
. He studied the mechanism of under-sensitive test structures and over-sensitive test structures. He pointed out that if this is properly understood, electrical failure analysis
Failure analysis
Failure analysis is the process of collecting and analyzing data to determine the cause of a failure. It is an important discipline in many branches of manufacturing industry, such as the electronics industry, where it is a vital tool used in the development of new products and for the improvement...
can be more easily achieved by electrical testing at the test structure level instead of at the product engineering level. This will make the job of DRAM yield enhancement easier.
Dr. Lau became an associate professor in the Nanyang Technological University
Nanyang Technological University
Nanyang Technological University is one of the two largest public universities in Singapore with the biggest campus in Singapore and the world's largest engineering college. Its lush 200-hectare Yunnan Garden campus was the Youth Olympic Village of the world's first 2010 Summer Youth Olympics in...
since 2001.
He was the first in making a correlation between the leakage current of ultrathin tantalum pentoxide (one of the high-k dielectric) films with defect states detected by zero-bias thermally stimulated current
Thermally stimulated current
Thermally stimulated current spectroscopy is an experimental technique which is used to study energy levels in semiconductors or insulators . Energy levels are first filled either by optical or electrical injection usually at a relatively low temperature, subsequently electrons or holes are...
. Most scientists cannot see any relationship between the leakage current in tantalum oxide (tantalum pentoxide) and the defect states detected by thermally stimulated current. For example, Dr. Yasushiro Nishioka (Japan) could not see any relationship between the leakage current and the defect states detected by thermally stimulated current (private communication). Dr. Lau managed to see the relationship between the leakage current and the defect states and published his theory in various papers. He invented "zero temperature gradient zero bias thermally stimulated current
Thermally stimulated current
Thermally stimulated current spectroscopy is an experimental technique which is used to study energy levels in semiconductors or insulators . Energy levels are first filled either by optical or electrical injection usually at a relatively low temperature, subsequently electrons or holes are...
" as a method to detect defect states in ultrathin high-k dielectric films. This was patented as US Patent 6909273 in 2005. (Please also see reference [9].) In addition, he has also developed a technique known as "two-scan zero-bias thermally stimulated current
Thermally stimulated current
Thermally stimulated current spectroscopy is an experimental technique which is used to study energy levels in semiconductors or insulators . Energy levels are first filled either by optical or electrical injection usually at a relatively low temperature, subsequently electrons or holes are...
" when an insulator or semiconductor has some traps which can be filled at low temperature and some traps which can only be filled at relatively high temperature. (Please see reference [10].)
He also worked on Cu/low-k
Low-K
In semiconductor manufacturing, a low-κ dielectric is a material with a small dielectric constant relative to silicon dioxide. Although the proper symbol for the dielectric constant is the Greek letter κ , in conversation such materials are referred to as being "low-k" rather than "low-κ"...
back-end-of-line (BEOL) technology. (Please see reference [11].)
He also wrote various papers on MOS transistors. For example, he worked on the application of strain engineering
Strain engineering
Strain engineering refers to a general strategy employed in semiconductor manufacturing to enhance device performance. Performance benefits are achieved by modulating strain in the transistor channel, which enhances electron mobility and thereby conductivity through the channel.-Strain...
to CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
technology. He pointed out that if tensile stress can increase the on current of n-channel MOS transistors, tensile stress will also increase the off current. Then he proposed a theory why tensile stress can improve n-channel MOS transistors even though there is an increase in the off current. A lady graduate student, Peizhen Yang, was recruited to work on research in this direction. (Please see references [12] & [13].) Similarly, his theory can be applied to the study of p-channel MOS transistors with the conventional <110> channel or the newer <100> channel. (Please see reference [14].) He also studied the reduction of boron lateral channelling (physics)
Channelling (physics)
Channelling is the process that constrains the path of a charged particle in a crystalline solid.Many physical phenomena can occur when a charged particle is incident upon a solid target, e.g., elastic scattering, inelastic energy-loss processes, secondary-electron emission, electromagnetic...
due to switching from the conventional <110> channel to the newer <100> channel.
Dr. Lau also studied the theory of electron mobility
Electron mobility
In solid-state physics, the electron mobility characterizes how quickly an electron can move through a metal or semiconductor, when pulled by an electric field. In semiconductors, there is an analogous quantity for holes, called hole mobility...
in Si-based MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
. In 2005, Dr. Lau pointed out as Lau's hypothesis that "remote Coulombic scattering" is only important in the subthreshold region and in the region slightly above threshold. (Please see reference [15].)
Dr. Lau also explained the observation of anomalous narrow channel effect in very short p-channel MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
. This effect is relatively weak in n-channel MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
. An explanation why this effect is strong in PMOS but weak in NMOS has been proposed by Dr. Lau; p-type dopants like boron tends to segregate into the STI oxide while n-type dopants tend to accumulate at the STI oxide/Si interface. (Please see references [16] & [17].)
Dr. Lau is also interested in quasi-ballistic transport
Ballistic transport
Ballistic transport is the transport of electrons in a medium with negligible electrical resistivity due to scattering. Without scattering, electrons simply obey Newton's second law of motion at non-relativistic speeds....
in MOS transistors and has published his theory on it. (Please see reference [18].) Instead of a carrier saturation velocity according to convention velocity saturation
Velocity saturation
In semiconductors, when a strong enough electric field is applied, the carrier velocity in the semiconductor reaches a maximum value, saturation velocity. When this happens, the semiconductor is said to be in a state of velocity saturation...
theory, an effective saturation velocity can be defined. It turns out that the value of effective saturation velocity in real-life MOS transistors is similar to established values of the carrier saturation velocity. However, Dr. Lau pointed out that the effective saturation velocity can be a function of the gate voltage.
Besides semiconductor materials and devices research, Dr. Lau also works privately on the research of traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...
, foot or hand reflexology
Reflexology
Reflexology, or zone therapy, is an alternative medicine involving the physical act of applying pressure to the feet, hands, or ears with specific thumb, finger, and hand techniques without the use of oil or lotion...
, "unrefreshing sleep", chronic fatigue syndrome
Chronic fatigue syndrome
Chronic fatigue syndrome is the most common name used to designate a significantly debilitating medical disorder or group of disorders generally defined by persistent fatigue accompanied by other specific symptoms for a minimum of six months, not due to ongoing exertion, not substantially...
, irritable bowel syndrome
Irritable bowel syndrome
Irritable bowel syndrome is a diagnosis of exclusion. It is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. In some cases, the symptoms are relieved by bowel movements...
, toothache
Toothache
A toothache, also known as odontalgia or, less frequently, as odontalgy, is an aching pain in or around a tooth.-Causes:* Dental etiology, In most cases toothaches are caused by problems in the tooth or jaw, such as** Dental caries...
, etc. For example, he noticed that there are two toothache
Toothache
A toothache, also known as odontalgia or, less frequently, as odontalgy, is an aching pain in or around a tooth.-Causes:* Dental etiology, In most cases toothaches are caused by problems in the tooth or jaw, such as** Dental caries...
mechanisms according to his personal experience: (A) Mechanism according to Western medicine and (B) Mechanism according to traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...
. He had direct experience of toothache
Toothache
A toothache, also known as odontalgia or, less frequently, as odontalgy, is an aching pain in or around a tooth.-Causes:* Dental etiology, In most cases toothaches are caused by problems in the tooth or jaw, such as** Dental caries...
which can be easily explained by Western medicine and also a kind of toothache
Toothache
A toothache, also known as odontalgia or, less frequently, as odontalgy, is an aching pain in or around a tooth.-Causes:* Dental etiology, In most cases toothaches are caused by problems in the tooth or jaw, such as** Dental caries...
which cannot be explained by Western dental theory but can be explained by traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...
. Thus the two mechanisms are not contradictory. They are actually complementary. The solution of the second kind of toothache
Toothache
A toothache, also known as odontalgia or, less frequently, as odontalgy, is an aching pain in or around a tooth.-Causes:* Dental etiology, In most cases toothaches are caused by problems in the tooth or jaw, such as** Dental caries...
is explained in various books on traditional Chinese medicine
Traditional Chinese medicine
Traditional Chinese Medicine refers to a broad range of medicine practices sharing common theoretical concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage , exercise , and dietary therapy...
. However, those solutions are too complicated or inconvenient for an ordinary person living in the Western World; Dr. Lau has privately developed a much simpler and convenient solution (unpublished). Dr. Lau is also interested in the application of Oldenlandia diffusa (a Chinese herb) to treat some medical problems.
He has also worked on the application of infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
to semiconductor materials. He has published a book "Infrared Characterization for Microelectronics", World Scientific
World Scientific
World Scientific Publishing is a publisher of scientific, technical, and medical books and journals. The company was founded in 1981 and now employs more than 200 staff at its headquarters in Singapore, with offices worldwide in New Jersey, California, London, New Delhi, Tianjin, Sydney, Hong...
, Singapore, 1999. He has also developed some new insight regarding the application of Raman spectroscopy
Raman spectroscopy
Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational, and other low-frequency modes in a system.It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range...
to health problems. He has also done some work on control theory
Control theory
Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems. The desired output of a system is called the reference...
and applied it to his research. The application of negative feedback
Negative feedback
Negative feedback occurs when the output of a system acts to oppose changes to the input of the system, with the result that the changes are attenuated. If the overall feedback of the system is negative, then the system will tend to be stable.- Overview :...
control to a chaotic system is highly challenging. He has developed some insight on the practical feedback control of chaotic systems.