handbook of modern sensors

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18.2 Surface Processing 543 sensor substrates are available from many manufacturers in thicknesses ranging from 0.1 to 10 mm. 18.1.5 Glasses Glass is an amorphous solid material made by fusing silica with a basic oxide. Although its atoms never arrange themselves into crystalline structure, the atomic spacing in glass is quite tight. Glass is characterized by transparency, availability in many colors, hardness, and resistance to most chemicals except hydrofluoric acid (Table A.25). Most glasses are based on the silicate system and is made from three major components: silica (SiO), lime (CaCO 3 ), and sodium carbonite (NaCO 3 ). Nonsilicate glasses include phosphate glass (which resists hydrofluoric acid), heat-absorbing glasses (made with FeO), and systems based on oxides of aluminum, vanadium, germanium, and other metals. An example of such specialty glass is arsenic trisulfate (As 2 S 3 ) known as AMTIR, which is substantially transparent in mid- and far-infrared spectral ranges and is used for fabricating infrared optical devices. 2 Borosilicate glass is the oldest type of glass which is substantially resistant to thermal shock. Under the trademark Pyrex ® , some of the SiO 2 molecules are replaced by boric oxide. The glass has a low coefficient of thermal expansion and thus is used for the fabrication optical mirrors (such as in telescopes). Lead–alkali glass (lead glass) contains lead monoxide (PbO) which increases its index of refraction. Also, it is a better electrical insulator. In the sensor technologies, it is used for fabricating optical windows and prisms and as a shield against nuclear radiation. Other glasses include alumosilicate glass (in which Al 2 O 3 replaces some silica), 96% silica, and fused silica. Another class of glass is light-sensitive glasses which are available in three grades. Photochromatic glass darkens when exposed to UV radiation and clears when the UV radiation is removed or glass is heated. Some photochromatic compositions remain darkened for a week or longer. Others fade within few minutes when UV radiation is removed. The photosensitive glass reacts to UV radiation in a different manner: If it is heated after exposure, it changes from clear to opal. This allows the creation of some patterns within the glass structure. Moreover, the exposed opalized glass is much more soluble in hydrofluoric acid, which allows for an efficient etching technique. 18.2 Surface Processing 18.2.1 Deposition of Thin and Thick Films Thin films are required to give a sensing surface some properties which it otherwise does not possess. For example, to enhance the absorption of thermal radiation by a farinfrared sensor, the surface may be coated with a material having high absorptivity, (e.g., nichrome). A piezoelectric film may be applied to a silicon wafer to give it piezoelectric properties. The thick films are often used to fabricate pressure sensors or microphones where the flexible membranes have to be produced. Several methods 2 AMTIR infrared glasses are available from Amorphous Materials, Inc. Garland, TX.
544 18 Sensor Materials and Technologies may be used to deposit thin and relatively thin (often referred to as “thick”) layers of films on a substrate or semiconductor wafer. Among them, the frequently used are the spin-casting, vacuum deposition, sputtering, electroplating, and screenprinting. 18.2.2 Spin-Casting The spin-casting process involves the use of a thin-film material dissolved in a volatile liquid solvent. The solution is pored on the sample and the sample is rotated at a high speed. The centrifugal forces spread the material, and after the solvent evaporates, a thin layer of film remains on the sample. This techniques is often used for the deposition of organic materials, especially for fabricating humidity and chemical sensors. The thickness depends on the solubility of the deposited material and the spin film and typically is in the range from 0.1 to 50 µm. Because the process relies on the flow of the solution, it may not yield a uniform film or can form island (filmfree areas) when the sample has a nonflat surface. In addition, the material may have tendency to shrink. Nevertheless, in many cases, it is a useful and often the only acceptable method of deposition 18.2.3 Vacuum Deposition A metal can be converted into gaseous form and then deposited on the surface of the sample. The evaporation system consists of a vacuum chamber (Fig. 18.5) where a diffuse pump evacuates air down to 10 −6 –10 −7 torr of pressure. A deposited material is placed into a ceramic crucible which is heated by a tungsten filament above the metal melting point. An alternative method of heating is the use of an electron beam. Fig. 18.5. Deposition of a thin metal film in a vacuum chamber.
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HANDBOOK OF MODERN SENSORS PHYSICS,
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HANDBOOK OF MODERN SENSORS PHYSICS,
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To the memory of my father
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Preface Seven years have passed sin
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Contents Preface ..................
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Contents XI 4.5 Lenses ............
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Contents XIII 7.7.1 Micropower Impu
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Contents XV 15 Radiation Detectors
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Contents XVII Table A.9 Physical Pr
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1 Data Acquisition “It’s as lar
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1.1 Sensors, Signals, and Systems 3
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1.1 Sensors, Signals, and Systems 5
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1.2 Sensor Classification 7 oscillo
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1.3 Units of Measurements 9 Table 1
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Table 1.7. SI Basic Units Reference
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2 Sensor Characteristics “O, what
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2.2 Span (Full-Scale Input) 15 Fig.
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2.4 Accuracy 17 2.4 Accuracy Avery
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2.6 Calibration Error 19 To compute
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2.8 Nonlinearity 21 Fig. 2.4. Trans
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2.12 Resolution 23 (A) (B) Fig. 2.7
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2.16 Dynamic Characteristics 25 2.1
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2.16 Dynamic Characteristics 27 Sub
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2.17 Environmental Factors 29 2.17
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2.18 Reliability 31 guide. For inst
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2.20 Uncertainty 33 • Thermal sho
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Table 2.2. Uncertainty Budget for T
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3 Physical Principles of Sensing
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3.1 Electric Charges, Fields, and P
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3.2 Capacitance 45 The capacitor ma
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3.2 Capacitance 47 (A) (B) Fig. 3.6
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3.2 Capacitance 49 h 0 (A) (B) Fig.
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3.3 Magnetism 51 N S S N (A) (B) Fi
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3.3 Magnetism 53 electric charge ca
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3.3 Magnetism 55 3.3.3 Toroid Anoth
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3.4 Induction 57 • Changing the o
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3.5 Resistance 59 Fig. 3.16. Voltag
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3.5 Resistance 61 For pure resistan
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3.5 Resistance 63 resistor) and the
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3.5 Resistance 65 Fig. 3.19. Strain
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3.6 Piezoelectric Effect 67 (A) (B)
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3.6 Piezoelectric Effect 69 Another
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3.6 Piezoelectric Effect 71 Another
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3.6 Piezoelectric Effect 73 absorpt
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3.6 Piezoelectric Effect 75 that en
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3.7 Pyroelectric Effect 77 circuit
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3.7 Pyroelectric Effect 79 through
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3.7 Pyroelectric Effect 81 Fig. 3.2
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3.8 Hall Effect 83 Fig. 3.30. Hall
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Table 3.2. Typical Characteristics
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3.9 Seebeck and Peltier Effects 87
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3.10 Sound Waves 93 If we consider
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3.11 Temperature and Thermal Proper
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3.11 Temperature and Thermal Proper
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3.12 Heat Transfer 99 to about 35
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3.12 Heat Transfer 101 (A) (B) Fig.
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3.12 Heat Transfer 103 Fig. 3.41. S
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3.12 Heat Transfer 105 Fig. 3.42. S
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3.12 Heat Transfer 107 Fig. 3.44. W
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3.12 Heat Transfer 109 (A) (B) Fig.
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3.13 Light 111 [38] whose emissivit
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3.14 Dynamic Models of Sensor Eleme
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References 119 specified and three
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References 121 34. Thomson, W. On t
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124 4 Optical Components of Sensors
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150 Optical Components of Sensors 1
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5 Interface Electronic Circuits 5.1
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5.1 Input Characteristics of Interf
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5.1 Input Characteristics of Interf
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5.2 Amplifiers 157 (A) (B) Fig. 5.5
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5.2 Amplifiers 159 Fig. 5.7. Voltag
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5.2 Amplifiers 161 (A) (B) Fig. 5.9
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5.2 Amplifiers 163 Fig. 5.11. An eq
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5.3 Excitation Circuits 165 5.3.1 C
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5.3 Excitation Circuits 167 (A) (B)
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5.3 Excitation Circuits 169 Fig. 5.
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5.3 Excitation Circuits 171 atures.
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5.3 Excitation Circuits 173 (A) (B)
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5.4 Analog-to-Digital Converters 17
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Table 5.2. Binary Bit Weights and R
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5.5 Direct Digitization and Process
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5.5 Direct Digitization and Process
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5.6 Ratiometric Circuits 191 (A) (B
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5.7 Bridge Circuits 193 determine t
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5.7 Bridge Circuits 195 Fig. 5.38.
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5.7 Bridge Circuits 197 Fig. 5.39.
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It can be solved for the temperatur
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5.8 Data Transmission 201 (A) (B) (
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5.8 Data Transmission 203 wire meth
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5.9 Noise in Sensors and Circuits 2
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5.10 Batteries for Low Power Sensor
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References 225 nickel-metal hydrate
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6 Occupancy and Motion Detectors Se
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6.2 Microwave Motion Detectors 229
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6.2 Microwave Motion Detectors 231
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6.3 Capacitive Occupancy Detectors
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6.3 Capacitive Occupancy Detectors
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6.4 Triboelectric Detectors 237 6.4
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6.5 Optoelectronic Motion Detectors
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and the facet pitch is 6.5 Optoelec
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References 251 Fig. 6.17. Calculate
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7 Position, Displacement, and Level
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7.1 Potentiometric Sensors 255 (A)
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7.2 Gravitational Sensors 257 (A) (
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7.3 Capacitive Sensors 259 (A) (B)
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7.3 Capacitive Sensors 261 Fig. 7.7
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7.4 Inductive and Magnetic Sensors
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7.5 Optical Sensors 275 Therefore,
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7.5 Optical Sensors 277 (A) (B) (C)
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7.5 Optical Sensors 279 (A) (B) Fig
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7.5 Optical Sensors 281 Fig. 7.32.
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7.5 Optical Sensors 283 (A) (B) (C)
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7.5 Optical Sensors 285 is proporti
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7.6 Ultrasonic Sensors 287 (A) (B)
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7.7 Radar Sensors 289 (A) (B) Fig.
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7.7 Radar Sensors 291 (A) (B) Fig.
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7.8 Thickness and Level Sensors 293
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References 299 8. Dakin, J. P., Wad
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8 Velocity and Acceleration Acceler
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8.1 Accelerometer Characteristics 3
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8.2 Capacitive Accelerometers 305 a
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8.3 Piezoresistive Accelerometers 3
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8.5 Thermal Accelerometers 309 Fig.
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8.5 Thermal Accelerometers 311 forc
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8.6 Gyroscopes 313 8.6 Gyroscopes N
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8.6 Gyroscopes 315 (A) (B) Fig. 8.1
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8.6 Gyroscopes 317 Products Company
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8.7 Piezoelectric Cables 319 (A) (B
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References 321 (A) (B) Fig. 8.16.Ap
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9 Force, Strain, and Tactile Sensor
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9.1 Strain Gauges 325 (A) (B) Fig.
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9.2 Tactile Sensors 327 9.2 Tactile
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9.2 Tactile Sensors 329 (A) (B) Fig
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9.2 Tactile Sensors 331 Fig. 9.7. P
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9.2 Tactile Sensors 333 Fig. 9.9. T
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9.3 Piezoelectric Force Sensors 335
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References 337 14. Karrer, E. and L
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10 Pressure Sensors “To learn som
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10.3 Mercury Pressure Sensor 341 1
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10.4 Bellows, Membranes, and Thin P
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10.5 Piezoresistive Sensors 345 Fig
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10.5 Piezoresistive Sensors 347 bri
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10.6 Capacitive Sensors 349 (A) (B)
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10.7 VRP Sensors 351 (A) (B) Fig. 1
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10.8 Optoelectronic Sensors 353 Fig
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10.9 Vacuum Sensors 355 (A) (B) Fig
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References 357 (A) (B) (C) Fig. 10.
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11 Flow Sensors It’s a simple tas
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11.2 Pressure Gradient Technique 36
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11.3 Thermal Transport Sensors 363
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11.3 Thermal Transport Sensors 365
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11.4 Ultrasonic Sensors 367 A senso
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11.4 Ultrasonic Sensors 369 Fig. 11
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induced in the liquid. The magnitud
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11.6 Microflow Sensors 373 (A) (B)
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11.7 Breeze Sensor 375 (A) (B) Fig.
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11.9 Drag Force Flow Sensors 377 Wi
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References 379 11. Philip-Chandy, R
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12 Acoustic Sensors “Your ears wi
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12.3 Fiber-Optic Microphone 383 (A)
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12.4 Piezoelectric Microphones 385
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12.5 Electret Microphones 387 Fig.
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12.6 Solid-State Acoustic Detectors
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References 391 References 1. Hohm,
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13 Humidity and Moisture Sensors 13
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13.1 Concept of Humidity 395 Table
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13.2 Capacitive Sensors 397 Fig. 13
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13.3 Electrical Conductivity Sensor
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13.4 Thermal Conductivity Sensor 40
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13.6 Oscillating Hygrometer 403 chi
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References 405 9. Jachowicz, R. S.
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14 Light Detectors “There is noth
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14.1 Introduction 409 Table 14.1. B
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14.2 Photodiodes 411 Maximum revers
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14.2 Photodiodes 413 when i = 0), w
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14.2 Photodiodes 415 (A) (B) (C) Fi
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14.2 Photodiodes 417 Fig. 14.9. Res
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14.3 Phototransistor 419 Fig. 14.12
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14.4 Photoresistors 421 (A) (B) Fig
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14.5 Cooled Detectors 423 (A) (B) F
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14.6 Thermal Detectors 425 Table 14
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14.6 Thermal Detectors 427 Fig. 14.
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Table 14.3. Typical Specifications
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14.6 Thermal Detectors 431 A dual e
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14.6 Thermal Detectors 433 Fig. 14.
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14.6 Thermal Detectors 435 (A) (B)
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14.6 Thermal Detectors 437 Section
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14.7 Gas Flame Detectors 439 P = V
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References 441 housing assures wide
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15 Radiation Detectors Figure 3.41
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15.1 Scintillating Detectors 445 Fi
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15.2 Ionization Detectors 447 emitt
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15.2 Ionization Detectors 449 Fig.
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15.2 Ionization Detectors 451 parti
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15.2 Ionization Detectors 453 There
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References 455 the pure intrinsic t
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16 Temperature Sensors When a scien
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16 Temperature Sensors 459 from whi
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16.1 Thermoresistive Sensors 461 2.
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16.1 Thermoresistive Sensors 463 Ta
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16.1 Thermoresistive Sensors 465 Fi
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16.1 Thermoresistive Sensors 467 pr
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16.1 Thermoresistive Sensors 475 (m
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16.2 Thermoelectric Contact Sensors
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16.3 Semiconductor P-N Junction Sen
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16.4 Optical Temperature Sensors 49
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Page 518 and 519: 17 Chemical Sensors 1 Chemical sens
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Page 536 and 537: 17.5 Complex Sensors 517 frequency
Page 538 and 539: Table 17.1. SAW Chemical Sensors 17
Page 540 and 541: 17.6 Chemical Sensors Versus Instru
Page 550 and 551: References 531 13. LaCourse, W.R. P
Page 552 and 553: 18 Sensor Materials and Technologie
Page 554 and 555: 18.1 Materials 535 etching is a key
Page 556 and 557: 18.1 Materials 537 Fig. 18.3. The a
Page 558 and 559: 18.1 Materials 539 The following is
Page 560 and 561: 18.1 Materials 541 should be consid
Page 564 and 565: 18.2 Surface Processing 545 On a co
Page 566 and 567: 18.3 Nano-Technology 547 6000-Å la
Page 568 and 569: 18.3 Nano-Technology 549 exposed to
Page 570 and 571: 18.3 Nano-Technology 551 Fig. 18.10
Page 572 and 573: 18.3 Nano-Technology 553 (A) (B) Fi
Page 574 and 575: References 555 Fig. 18.17. Bonding
Page 576 and 577: Appendix Table A.1. Chemical Symbol
Page 578 and 579: Table A.4. SI Conversion Multiples
Page 580 and 581: Table A.4 Continued Light cd/in. 2
Page 582 and 583: Table A.4 Continued Cup 2.36588 ×
Page 584 and 585: Appendix 565 Table A.7. Some Materi
Page 586 and 587: Appendix 567 Table A.11. Thermoelec
Page 588 and 589: Table A.14. Mechanical Properties o
Page 590 and 591: Appendix 571 Table A.18. Typical Em
Page 592 and 593: Table A.20. Characteristics of C-Zn
Page 594 and 595: Table A.23 Continued Manufacturer P
Page 596 and 597: Table A.25. Properties of Glasses S
Page 598 and 599: Index α-particles, 443 A/D, 175, 1
Page 600 and 601: Index 581 Coulomb’s law, 40 cross
Page 602 and 603: Index 583 H 2 O, 108 Hall, 82 Hall
Page 604 and 605: Index 585 occupancy sensors, 227 od
Page 606 and 607: Index 587 SAW, 75, 388, 404, 496, 5
Page 608: Index 589 velocity sensor, 302 vert
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