RU2614738C1 - Resistive material based on non-stoichiometric sulphides - Google Patents

Abstract

FIELD: electronics.

SUBSTANCE: invention relates to radio- and microelectronics and can be used in microelectronic equipment with low values of currents and voltages, which requires switching within time intervals from 25 to 110 minutes at 10–150 °C. Resistive material contains silver sulphide, non-stoichiometric germanium sulphide and non-stoichiometric arsenic sulphide according to empirical formula: 0.5(Ag₂S)⋅(Ge_1+xS)⋅0.5(As_2-2xS₃), where 0.4≤x≤0.8.

EFFECT: material shows declared properties: functional dependence of resistance on the application time of constant difference in potentials, has time periods of electric conductivity relaxation from 70 to 196 seconds and the value of specific electrical resistance of about 10⁵–10⁶ Ohm⋅m, within temperature range of 10–150 °C.

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Description

The invention relates to radio and microelectronics and can be used in the manufacture of electronic devices, elements of electronic circuits with a functional dependence of electrical resistance on time, operating in the temperature range of 10-150 ° C.

Known resistive material with a functional dependence of electrical resistance on time, containing silver selenide, germanium selenide and arsenic selenide (RF patent No. 2066076, IPC6 НСС 7/00, publ. 08/27/1996).

The disadvantage of this material is the small, in comparison with the known from the prior art, the value of electrical resistivity.

The closest in technical essence to the present invention is a resistive material with a functional dependence of electrical resistance on time, containing silver sulfide, arsenic sulfide and germanium sulfide (RF patent No. 179192, IPC6 H01C 7/00, publ. 12/27/1996).

Patented resistive material differs from the prototype in that it contains non-stoichiometric germanium sulfide and non-stoichiometric arsenic sulfide, the addition of which affects the obtained technical result. In particular, the value of electrical resistivity increases by an order of magnitude, and the relaxation time of electrical resistance increases to ~ 100 minutes.

The objective of the invention is to create a resistive material with a functional dependence of the resistance on time with a large (table. 1 Fig. 1) time to establish current and a large (table. 1 Fig. 1) resistance for use in microelectronic equipment with low values of currents and voltages (resistors with time-dependent resistance, switches, etc.), where switching is required for periods of 25-110 minutes at 10-150 ° C.

The problem is achieved due to the fact that the resistive material contains non-stoichiometric germanium sulfide and non-stoichiometric silver sulfide and corresponds to the general formula 0.5 (Ag ₂ S) ⋅ (Ge _{1 + x} S) ⋅ 0.5 (As _2-2x S ₃ ) where 0.4≤x≤0.8. Specific examples of the invention are presented in table. 2 (Fig. 2).

There is a causal relationship between the totality of the essential features of the claimed object and the achieved technical result, namely, the non-stoichiometry of germanium and arsenic sulfides in the synthesis provides such material properties as electrical resistivity of the order of 10 ⁵ -10 ⁶ Ohm⋅m, electrical relaxation time of 11- 100 minutes, conductivity relaxation time 70-196 seconds, current settling time 25-110 minutes.

The proposed resistive material is obtained from the starting components taken in the form of pure elements (silver, germanium, arsenic, sulfur) in amounts corresponding to the above general formula, by sintering at a certain temperature.

Example. x = 0.4. Metallic silver in an amount of 4.3143 g, germanium in an amount of 4.0651 g, arsenic in an amount of 1.7978 g, sulfur in an amount of 4.0647 g are sintered in an atmosphere of inert gases at specially selected temperatures. The finished product meets the general formula 0.5 (Ag ₂ S) ⋅ (Ge _{1 + x} S) ⋅0.5 (As _2-2x S ₃ ), where 0.4≤x≤0.8, and is a homogeneous ingot a reddish hue with a metallic luster and a conchoid fracture characteristic of glassy materials, transparent to light with a thickness of less than 0.5 mm.

Similarly received samples of resistive material, the compositions of the initial mixture and the final product of which are given in table. 2 (Fig. 2).

To measure the electrical characteristics of the resistive material from the obtained ingots, samples were prepared in the form of rectangular parallelepipeds. The polarization dependences of the electrical resistance on time were measured by the two-electrode method when a constant potential difference with the indicated polarity was applied to an asymmetric cell with a sample:

+ reversible electrode | sample | blocking ion component electrode | -

In FIG. Figure 3 shows the curves of the electrical resistivity of a patented resistive material versus time at 27 ° C. Dependence 1 refers to the composition with x = 0.5, dependence 2 - to the composition with x = 0.6.

In FIG. 4 shows the dependence of the electrical conductivity of the patented resistive material (x = 0.8) on time at 27 ° C.

The process of a smooth drop in current strength and an increase in electrical resistance with time is due to the gradual suppression of the ionic component of conductivity due to the polarization phenomenon. In this case, mobile silver ions are concentrated near a negatively charged electrode, creating a concentration gradient over the sample. The presence of a concentration gradient of positively charged silver ions leads to the appearance of a diffusion ion flux directed in the opposite direction with respect to the drift ion flux. In the stationary state, the drift and diffusion fluxes of ions cancel each other and only the electron current flows through the sample. Consequently, the conductivity of the sample decreases from its value at time zero, corresponding to the total (ionic and electronic) conductivity, to a value equal to the electronic conductivity in a steady polarized state. The potential difference applied to the sample is selected less than the value at which the electrolysis of the material begins.

до момента времени, когда электросопротивление достигает 90% от величины установившегося при больших временах приложения постоянной разности потенциалов. Под временем релаксации электропроводности будем понимать время, в течение которого электропроводность уменьшается от своего начального значения в момент времени приложения постоянной разности потенциалов к ячейке t₀ в е раз. За величину времени установления тока принимали промежуток времени от момента t₀ до момента выхода электросопротивления на стационарное состояние (почти не изменяется).From the analysis of FIG. 3 and FIG. Four polarization dependences were evaluated for the relaxation time of the electrical resistance, the relaxation time of the electrical conductivity, and the settling time of the current. During the relaxation of electrical resistance, as in the prototype (RF patent No. 179192, IPC6 НСС 7/00, publ. 12/27/1996), the time interval from the moment of applying a constant potential difference to the cell was taken

up to the point in time when the electrical resistance reaches 90% of the value of the constant potential difference established during long times of application. Under conductivity relaxation time we mean the time during which the electrical conductivity decreases from its initial value at the time point of constant potential difference to t ₀ cell in e. For the value of the current settling time, we took the time interval from the moment t ₀ until the moment the electrical resistance reaches the stationary state (almost does not change).

, где t₁ и t₂ - два времени релаксации, одно из которых (меньшее) характеризует процессы релаксации в приэлектродных слоях образца, а второе (большее) характеризует процессы релаксации, связанные с особенностями атомной структуры материалов (Н.В. Мельникова, К.В. Курочка, О.Л. Хейфец, Н.И. Кадырова, Я.Ю. Волкова. Известия РАН. Серия физическая. - 2015. - Т. 79, №6. - С. 790-794). Усредненное время релаксации электропроводности рассчитывалось путем аппроксимации поляризационных зависимостей экспоненциальной функцией

(τ - усредненное время релаксации электропроводности).The relaxation times of the electrical conductivity of the patented materials were obtained from the approximation by the exponential function of the dependences of the electrical conductivity on the time of application of a constant potential difference to the cell. The polarization curves of the electrical conductivity of patented materials are well analytically described by the double exponential formula

, where t ₁ and t ₂ are two relaxation times, one of which (lesser) characterizes the relaxation processes in the electrode layers of the sample, and the second (more) characterizes relaxation processes associated with the peculiarities of the atomic structure of materials (N.V. Melnikova, K. V. Kurochka, O. L. Kheyfets, N. I. Kadyrova, Y. Yu. Volkova. Izvestia RAS. Physical Series. - 2015. - T. 79, No. 6. - S. 790-794). The average relaxation time of the electrical conductivity was calculated by approximating the polarization dependences by an exponential function

(τ is the average relaxation time of the electrical conductivity).

The results of measuring the electronic and ionic components of the conductivity at 27 ° C, as well as the values of the relaxation time of the electrical resistance, the relaxation time of the electrical conductivity (τ) and the current settling time for compositions with different x values are given in Table. 2 (Fig. 2).

The results of the study of the share of the electronic component of conductivity, the value of electrical resistivity, relaxation time of electrical resistance and the range of operating temperatures in the claimed material and in the material that is the prototype are presented in table. 1 (Fig. 1).

From the table. 1 (Fig. 1) it follows that the value of the electrical resistance of materials 0.5 (Ag ₂ S) ⋅ (Ge _{1 + x} S) ⋅0.5 (As _2-2x S ₃ ) exceeds the electrical _{resistance of} materials that are a prototype, by an order of magnitude and the relaxation time of the electrical resistance of the patented materials is significantly longer than the relaxation time of the electrical resistance of the materials that are the prototype.

Such an increase in the resistance value allows the use of the inventive materials as resistors in microelectronic equipment with small values of currents and voltages, where a functional dependence of the resistance on time, large resistance values and long relaxation times at 10-150 ° C are required.

Claims (3)

Resistive material containing silver, germanium and arsenic sulfides, characterized in that it contains non-stoichiometric arsenic sulfide and non-stoichiometric germanium sulfide according to the empirical formula: 0.5 (Ag ₂ S) ⋅ (Ge _{1 + x} S) ⋅ 0.5 (As _2-2x S ₃ ), where 0.4≤x≤0.8.

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