RU2021591C1 - Device for measurement of biological, biochemical, chemical and physical parameters of medium - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: electromagnetic radiation flux excites surface electromagnetic wave in metal film located on substrate made of semiconductor material. In this case investigated medium is placed in zone of propagation of electromagnetic radiation and/or of surface electromagnetic wave. Signal registered in circuit between metal film and semiconductor layer characterizes corresponding parameter of investigated medium. EFFECT: improved authenticity of measurements. 14 cl, 8 dwg

Description

 The invention relates to a non-contact method for studying the characteristics of an environment, mainly of biological origin and / or in contact with biological objects of the environment, the parameters of which determine the vital activity of these biological objects, and can be used to determine the composition and properties of media containing chemical and biological components, for scientific research and control of technological processes, in particular in microbiology, immunology, chemistry and biochemistry, for environmental monitoring.

 A device for measuring environmental parameters containing an electric discharge cell and a photo-recording unit. As a result of registering the shape of the corona, the researcher can judge the magnitude of some parameters by correlating the information received with the control images.

 The disadvantage of this device is that it is unsuitable for the study of biological environments, because with the specified impact on the biological environment, the probability of destruction of this environment is high.

 Also known is the device that is closest to the declared one for measuring environmental parameters, mainly for biological or biophysical studies, containing a source of electromagnetic radiation, a solid-state structure consisting of a metal film deposited on a substrate for excitation in the last surface electromagnetic wave (SEW), and information processing unit.

 The advantage of this device is that the parameter measurements can be carried out without destroying any medium or without any undesirable effects on the medium.

 However, in this device, the presence of a special built-in channel for measuring an optical signal associated with a radiation beam reflected from a metal film is fundamental. This channel contains a special optical circuit and a photoconverter. The presence of such a channel makes the device expensive and difficult to operate, and prevents the minimization of its dimensions. In addition, the fixed arrangement of the elements of the said measuring channel extremely narrows the scope of this device and the range of measured parameters. The transition to flexible circuits of the measuring channel of the reflected signal extremely complicates the device and its use, reduces the accuracy of the measurements. These factors are significant disadvantages of this device.

 The aim of the invention is to improve the operational parameters of the device, in particular its simplicity, convenience, compactness and low cost by achieving the possibility of mass production on the basis of industrial microelectronics technologies, as well as improving the accuracy and resolution of measurements, expanding the range of applicability and range of measured parameters.

 This goal is achieved in that the substrate is made of semiconductor material, and the inputs of the information processing unit are connected directly to the metal film and the substrate. The film and the substrate are adjacent to each other directly or through an intermediate layer, the resistivity of which exceeds the resistivity of the aforementioned metal film, and the interface in both cases can be partially or fully spatially modulated.

 The source of electromagnetic radiation can be configured to readjust the frequency of radiation and / or to change the direction of propagation of the electromagnetic wave from this source relative to the position of said solid state structure.

 To ensure the SEW excitation, the surface of the metal film from the side opposite to the location of the semiconductor layer is spatially modulated, or the device is equipped with a means (for example, a prism) to ensure complete internal reflection from its output face. This face can be set with a gap relative to the surface of the metal film in such a way that a layer of a substance is located in the said gap, the refractive index of which is less than the refractive index of the medium of said medium.

 To increase the accuracy and selectivity of measurements on or above the surface of the metal film from the side opposite to the location of the semiconductor layer, a substance layer can be located with predetermined dependences of its parameters on the magnitude and type of external influence, in particular on the influence of the medium under study. The device may be provided with at least one layer for bonding at least one component of the sample, and this layer is located on or above the surface of the metal film.

 The device can be introduced into the test medium or be equipped with a volume for the test medium, part of which, located in the zone of passage of the electromagnetic radiation flux, in some cases it is advisable to perform in the form of a wedge.

 In addition, the device may be equipped with a means for polarizing the flow of electromagnetic radiation and an optical fiber for supplying a flow of electromagnetic radiation.

 This embodiment of the device makes it possible, by combining the metal film with the semiconductor substrate, to exclude the registration channel of the reflected optical signal and to directly register the electrical signal corresponding to the values of the studied medium parameters. This allows not only to expand the scope of the device, since in this case the dimensions of the device are significantly reduced, but also significantly simplify the work with it, increase the accuracy and range of measurements, and sharply reduce the cost of the device. The device as a whole (not counting the registration unit) takes the form of an optoelectronic pair - a hybrid circuit, parts of which, emitting and receiving, are realizable on the basis of mass industrial microelectronic production.

 In FIG. 1-3 schematically presents the claimed device with options for the excitation of surface electromagnetic waves (SEW) through spatial modulation (lattice) on the metal surface; in FIG. 4-8 - with options for the excitation of SEW by the method of impaired total internal reflection, while in FIG. 1 test medium is placed in a special cuvette, one of the walls of which is the surface of a sensitive solid-state structure; in FIG. 2 - in a wedge-shaped cell, removable or non-removable, located at some distance from the surface of the sensitive solid-state structure; in FIG. 3 - the same without a cuvette, when the measuring head itself is introduced into the test medium; in FIG. 4 - shows the radiation supply from the side of the semiconductor substrate, the latter being a semiconductor layer deposited on the output face of the prism (the measuring head may or may not be supplied with a cuvette); in FIG. 5 - wedge-shaped cell, removable or not removable; in FIG. 6 - the same without a cuvette, when the measuring head itself is introduced into the test medium; in FIG. 7 and 8 are cases when the total internal reflection of radiation comes from the output boundary of the test medium, and in FIG. 7 shows a cuvette embodiment for a test medium; in FIG. 8 - the measuring head itself is introduced into the test medium.

 A device for measuring environmental parameters comprises a measuring head 1, an information processing and display unit 2, and connecting wires 3 and 4. The measuring head is made according to the principle of an optoelectronic pair — a radiation source and receiver.

 As the source 5 of electromagnetic radiation (usually visible or infrared), it is preferable to use a built-in semiconductor emitter or output end of the optical fiber, which ensures the compactness of the measuring head.

A solid-state structure 6 is used as a radiation detector. Its main elements are a metal film 7 (for example, Ag, Au, Al, Cu) and a semiconductor substrate 8 (for example, Si, GaAs, InP). The wire 3 is connected directly to the metal film 7, the wire 4 is connected to the substrate 8 through an ohmic contact 9. The structure 6 can also contain a thin intermediate layer 10 (for example, SiO ₂ ) between the film 7 and the substrate 8, which is sometimes introduced to increase the electrical resistance of the metal semiconductor and is not essential from the point of view of the principle of operation of the proposed device. The interface between the metal 7 and the semiconductor 8 or at least one of the surfaces of the layer 10 can be spatially modulated (for example periodically profiled) to enhance the scattering of SEWs from the metal 7 into the semiconductor 8. For excitation of the SEW by the lattice method on the surface of the metal film 7 not facing the semiconductor , this surface is spatially modulated, for example, in the form of a sinusoidal lattice (Fig. 1-3). To excite the SEW by the method of impaired total internal reflection in the schemes of FIG. 5 and 6, a prism 11 is used, which is rigidly fixed relative to the structure 6 according to the standard Otto SEW excitation method, forming a gap 12 filled with air or another dielectric (in particular, the medium under test 13) with a lower refractive index than that of the prism. The diagrams of FIG. 7 and 8 also use the Otto method, but the wedge-shaped layer of the test medium 13 located on the path of the radiation beam plays the role of a prism, the refractive index of which is obviously larger than that of the substance in the gap 12. In the diagram of FIG. 4, the gap between the prism 11 and the film 7 is filled with a layer of a semiconductor material representing a substrate 8. The circuit obtained in this way corresponds to the Kretschmann method of excitation of SEW. In the case of the substrate material 8, weakly absorbing the radiation of the source 5, the layer 8 and the prism 11 can be a single volume of the semiconductor.

 The radiation source 5 may be adjustable in frequency and / or in the direction of radiation relative to the structure 6. In FIG. 1-8 schematically shows the possibility of angular displacement and reading of the angle by means of an angular scale 14 with a nonius 15. By scanning in frequency and moving along the angle of the radiation source, the device can be adjusted and adjusted, and control dependencies can be removed. Instead of an angular scale and a nonius, it is advisable to use a potentiometric sensor for the angular position of the radiation source. It allows you to convert the value of the angle into a volt signal and, for example, on a two-coordinate recorder, immediately obtain the dependence of the information signal on the angle for any method of scanning by angle. At the output of the radiation from the source 5, a polarizer and a micro lens can be provided.

 For all variants of the device, it is essential that the test medium 13 is located relative to the structure 6 from the side of the metal film. In all embodiments except FIG. 4, medium 13 lies in the path of the radiation beam from source 5 to film 7.

 In the diagrams of FIG. 1, 3 and 4, the medium 13 can either come into contact with the film 7 or be separated from it by the intermediate layers 16 and 17. The material of the layer 16 can be a substance that reacts in a predetermined manner to the action of the test medium 13, in particular, binding (adsorbing or absorbent) component of the medium 13, the parameters of which you want to measure. Layer 17 may be intended for auxiliary purposes, for example, to protect the film 7 or layer 16 from the aggressive components of the medium 13, to improve the adhesion of the layer 16, etc.

 In the diagrams of FIG. 5-8, the medium 13 is not in contact with the film 7, unless in the circuits of FIG. 5 and 6, the medium 13 has a lower refractive index than that of the prism 11 and also fills the gap 12. In these cases, as well as in the diagrams of FIG. 7 and 8, the gap 12 may also contain layers 16 and 17, with corresponding restrictions on their thickness and refractive indices.

 In the diagrams of FIG. 2 and 5, when the medium 13 is removed from the film 7 by distances significantly exceeding the penetration depth of the SEW, and the medium on the radiation path in front of the cell 18 and after it is the same, it is necessary that the medium layer 13 lying on the radiation path from the source 5 to the film 7, had the shape of a wedge. The shape of the wedge provides a dependence of the excitation conditions of the SEW in the film 7 on the refractive properties of the medium 13.

 The energy of the radiation quantum of the source 5 can be both greater and less than the band gap of the semiconductor.

 The embodiment of the device shown in FIG. 4, it is expedient for studying weakly transparent and scattering media similarly, without transmitting radiation through them, by means of only SEWs whose energy density decreases exponentially in medium 13.

 The device operates as follows.

=

- волновой вектор падающего излучения частотой ω и длиной волны λв вакууме;
n - показатель преломления тестируемой среды 13;
n_призмы - показатель преломления призмы 11 на фиг. 5 и 6, материала полупроводниковой подложки 8 на фиг. 4, среды 13 на фиг. 7 и 8;
θ - угол падения излучения на решетку в (1) (фиг. 1-3) или на выходную грань призмы в (2) фиг. 4-8);
m - целое число m≠0);
G =

- обратный вектор решетки периода Λ ;
R_пэв - волновой вектор ПЭВ.SEWs on the surface of the film of metal 7, not facing the substrate 8, are excited by converting the p-polarized component of the incident electromagnetic radiation by means of a lattice on this surface of the film 7: Rn sin θ + mG = R _pev (1) or prism 11 Rn of the _prism sin θ = R _pav (2). where R =

=

- wave vector of incident radiation with frequency ω and wavelength λ in vacuum;
n is the refractive index of the test medium 13;
n _prisms is the refractive index of prism 11 in FIG. 5 and 6, the semiconductor substrate material 8 in FIG. 4, medium 13 in FIG. 7 and 8;
θ is the angle of incidence of radiation on the grating in (1) (Figs. 1-3) or on the output face of the prism in (2) of Figs. 4-8);
m is an integer m ≠ 0);
G =

is the inverse lattice vector of the period Λ;
R _pev - wave vector SEW.

$\genfrac{}{}{0ex}{}{\text{("+"}}{\text{("-"}}$ $\genfrac{}{}{0ex}{}{\text{для}}{\text{для}}$ $\genfrac{}{}{0ex}{}{\text{m>0,}}{\text{m<0)}}$
(3)
Здесь, в свою очередь, ε'_Me - действительная часть диэлектрической проницаемости металла на частоте ω (обычно ε_Me<0, | ε'_Me| >>1).In the simplest case, at the interface between two media - a metal and a dielectric - it is described by the expression:
R _pev = ±

$\genfrac{}{}{0ex}{}{\text{("+"}}{\text{("-"}}$ $\genfrac{}{}{0ex}{}{\text{for}}{\text{for}}$ $\genfrac{}{}{0ex}{}{\text{m> 0,}}{\text{m <0)}}$
(3)
Here, in turn, ε ' _Me is the real part of the dielectric constant of the metal at a frequency ω (usually ε _Me <0, | ε' _Me | >> 1).

In the diagrams of FIG. 1-4, when additional layers are not applied on the surface of the film 7, R _{pev is} described by expression (3), but in the circuit of FIG. 2 instead of n, we must substitute the refractive index of the medium adjacent to the film 7 (usually air).

In the diagrams of FIG. 5-8 without layers 16 and 17 R _{pev is} described by expression (3) with n replaced by the refractive index of the dielectric in the gap 12 and does not depend on n medium (except when the medium 13 is not isolated from the gap 12).

In the case of a multilayer system (film 7 — layers 16 and 17) the dependence of R _pev on (n of the medium is described in a more complex way and is less pronounced. R _pev in such a system strongly depends on the refractive indices of layers 16 and 17.

Equalities (1) and (2) describe the position of the resonance maximum of the conversion efficiency (the fraction of the radiation energy converted to SEW energy) depending on R, n and θ. The dependence of the resonance position on n medium in the circuits of FIG. 1, 3, 7 and 8, as well as FIG. 5 and 6, in cases when the medium 13 is filled with a gap 12, it is expressed both through the tangential component Rn sinθ of the wave vector of the incident radiation, and through R _pev . In the diagrams of FIG. 2 as well as FIG. 5 and 6 with a gap 12 isolated from the medium 13 - only through Rn sinθ, i.e., through the magnitude and (or) the direction of the wave vector of the incident radiation. In the circuit of FIG. 4 - only through R _pev ). When any of these parameters (for example, n) is changed, the position of the resonance changes (the resonance values are R and θ; when this parameter changes, the conversion efficiency changes sharply within the width of the resonance curve.

 In schemes where the conversion efficiency depends on the test medium only through Rn sin θ, this device can be used as a sensor of the refractive index of a medium or a parameter directly related to it (for example, the concentration of a known component in a solution), i.e., as a refractometric medium sensor . Schemes with a sensitive layer 16 give, in addition, the ability to measure, through the dependence of the conversion efficiency on the optical properties of this layer, any medium parameter 13 that can affect the latter. In particular, the appropriate choice of material of the layer 16 makes it possible to measure the concentration of the required component of the medium in a selective manner.

 The excitation of the SEW is accompanied by the generation of an electrical signal (voltage or current), which, through pins 3 and 4, enters the inputs of the information processing unit 2. Its value is directly related to the value of the conversion efficiency of radiation into SEW. There are various mechanisms for generating such a signal. If the radiation quantum energy is greater than the semiconductor band gap, then the formation of electron-hole pairs in the semiconductor is possible by absorbing part of the SEW energy in the semiconductor either directly or through radiative scattering at the metal-semiconductor interface. If the energy of the radiation quantum is less than the band gap of the semiconductor, then the formation of hot carriers in the metal due to the absorption of SEW energy and their emission into the semiconductor is possible. In both cases, the carrier current under the action of the potential metal-semiconductor barrier field leads to an electric response, as in a conventional photodetector.

 Thus, the resonance of the value of the conversion efficiency of radiation in SEW is accompanied by the resonance of the electrical signal at the inputs of the processing unit 2. Studying the magnitude and features of the dependences of this signal on ω, θ or on the direction of radiation polarization at various values of the medium parameters and comparing the obtained characteristics with the control ones, we obtain information on the values of the mentioned parameters. In addition, if the device is configured so that the magnitude of the electrical signal corresponds to the slope of the resonance curve, then with changes in the studied parameter of the medium, which does not bring the system beyond the limits of resonance, the device operates as a direct optoelectronic converter of the measured quantity into an electrical signal. After appropriate calibration, the measured values can be directly read from the display of block 2.

 The invention allows for quick and convenient measurement of medium parameters by compact means that do not use complex optical schemes, suitable not only in laboratory, but also in industrial, field and domestic conditions. It also allows for the implementation of low-cost production of optoelectronic means for measuring medium parameters based on industrial microelectronics technology.

Claims (14)

 1. DEVICE FOR MEASURING BIOLOGICAL, BIOCHEMICAL, CHEMICAL OR PHYSICAL MEDIA PARAMETERS, containing an electromagnetic radiation source, a solid-state structure consisting of a metal film deposited on a substrate for excitation in the last surface electromagnetic wave, as well as an information processing unit, characterized in that the substrate is from a semiconductor material, and the inputs of the information processing unit are connected with a metal film and a substrate.  2. The device according to claim 1, characterized in that the interface between the metal film and the semiconductor material is partially or fully spatially modulated.  3. The device according to claim 1, characterized in that between the metal film and the semiconductor material there is an intermediate layer, the resistivity of which exceeds the resistivity of said metal film.  4. The device according to claims 1 and 3, characterized in that at least one of the surfaces of the said intermediate layer is partially or fully spatially modulated.  5. The device according to claim 1, characterized in that the source of electromagnetic radiation is configured to be tuned according to the frequency of radiation.  6. The device according to claim 1, characterized in that it is arranged to change the position of said solid state structure relative to the direction of propagation of the electromagnetic wave from the source of electromagnetic radiation.  7. The device according to claim 1, characterized in that the surface of the metal film from the side opposite to the location of the semiconductor layer is spatially modulated.  8. The device according to claim 1, characterized in that it is equipped with a means for ensuring complete internal reflection of radiation from its output face.  9. The device according to claims 1 and 8, characterized in that the output face of the said means forms a gap with the surface of the metal film, in which there is a layer of a substance whose refractive index is less than the refractive index of the medium of the said means.  10. The device according to claim 1, characterized in that on the surface of the metal film or above it from the side opposite to the location of the semiconductor layer, there is a layer of substance with predetermined dependences of its parameters on the size and type of external influence.  11. The device according to claim 1, characterized in that it is provided with at least one layer for bonding at least one component of the medium, and this layer is located on the surface of the metal film or above it.  12. The device according to claim 1, characterized in that it is provided with a volume for the test medium, a part of which is located in the zone of passage of the electromagnetic radiation flux, made in the form of a wedge.  13. The device according to claim 1, characterized in that it is equipped with a means for polarizing the flow of electromagnetic radiation.  14. The device according to claim 1, characterized in that it is equipped with an optical fiber for supplying a stream of electromagnetic radiation.

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