Introduction

At the present time, there are many works in the field of creating various nanostructured objects. One of the directions in this area is the formation of nanoparticles of various metals, which have unique properties that differ from bulk materials due to surface and quantum-confinement effects that appear when the size of the object decreases. This makes it possible to significantly increase the application field of such materials.

One example of such materials is indium (In) nanoparticles. Thus, in the transition from the bulk state to the nanoscale, a decrease in the melting point of indium is observed [1]. This allows the use of indium as seed particles in the process of growth of one-dimensional semiconductor structures both by low-temperature methods (liquid–liquid-solid LLS) [1,2,3] and by high-temperature methods (vapor–liquid-solid VLS) [4, 5]. At the same time, the size of indium particles impacts on diameter of one-dimensional structures [5, 6]. Therefore, it is important to obtain indium particles of certain sizes. Also, due to the low melting point and the electron work function, it is possible to use indium particles as one of the components for composite materials used in non-volatile memory devices [7]. In addition, indium nanoparticles exhibit surface plasmon resonance in the ultraviolet range [8, 9], which can be used in the method of molecular spectroscopy called surface-enhanced Raman spectroscopy (SERS) in the UV region for ultra-sensitive and ultra-low determination of concentration of the analyzed substance [10], photovoltaics devices [11, 12], and in biotechnologies for detecting DNA hybridization [13]. Due to the optical absorption in the infrared range [14], it is possible to use indium nanoparticles in photothermal therapy for the treatment of oncological diseases [15]. Indium particles are also used for the synthesis of InP [4, 16] applied in the electronics industry.

There are many ways to form indium particles: physical and chemical. There are such methods as thermal evaporation [17] followed by annealing and reduction in hydrogen atmosphere [18], laser ablation [19], pulsed plasma in liquid [20], chemical reduction [21], and electrochemical deposition [22, 23], including deposition from non-aqueous solutions, for example, based on dimethoxyethane or polyethylene glycol with the addition of indium (III) bis(trifluoromethanesulfonyl)imide [24], etc.

Among the large variety of methods for obtaining indium particles, it is more profitable to use low-temperature and vacuum-free methods that do not require expensive equipment, such as, chemical and electrochemical deposition methods. In this case, the most promising is one of the varieties of electrochemical deposition methods using aqueous solutions. In this way, the presence of toxic or expensive substances for synthesis is not required, but such substances are often necessary during precipitation from ionic liquids or chemical reduction [21, 22]. At the same time, it is possible to form particles of different sizes for various applications due to the possibility of varying deposition parameters in a wide range [23].

However, the articles mostly consider the final film structure rather than the particles, and therefore, no information is presented on how a particular process parameter affects the geometrical parameters of the particles. Consequently, the aim of the present work is to study the morphology of In particles obtained by electrochemical deposition from an aqueous solution depending on various parameters of their formation.

Experimental

Material preparation

Fifty-micrometer titanium foil (99.9%) was used as a substrate for electrochemical deposition of indium. The sizes of substrates were 4 × 5 cm. These substrates were previously cleaned in a mixture of 100 ml hydrogen peroxide (37% H2O2, > 70%, Peroxid), 100 ml an ammonium hydroxide solution (25% NH3 basis, ≥ 99%, Sigma Tec) solution, and 400 ml deionized water for 15 min. After that, they were washed in hot and in cold deionized water (resistivity 18.2 MΩ cm) for 5 min. Then, the substrates were dried and etched in a mixture of 30 ml hydrofluoric acid (40% HF, > 98%, Sigma Tec), 20 ml nitric acid (70% HNO3, 99%, Mosreaktiv), and 150 ml of deionized water for 5 s, then washed in deionized water and dried in an air stream. Then, a chromium sublayer was applied to substrates using the magnetron sputtering. The thickness of the layer was about 100 nm. Deposition was carried out on the URM-026. Before the start of the process, the vacuum chamber was evacuated to a residual pressure not worse than 7·10−5 Torr. The surface of titanium foil was subjected to preliminary bombardment with argon ions using ion source AI-4–015 (ion current 40 mA, processing time—120 s) in order to remove residual contaminants and surface oxide. Chromium target (Cr 99.95%, LLC “Kermet”) was atomized in argon gas environment (argon volume fraction not less than 99.9999%) at a pressure of 3·10−3 Torr. The sputtering power of the chromium target was 1000 W. The obtained titanium substrate with chrome sublayer (Ti-Cr) was placed in an exicator to prevent surface contamination, where it was stored before the experiments.

Arrays of indium particles were formed using the electrochemical deposition method. Electrochemical deposition of indium was carried out in a three-electrode cell. The working electrode was the titanium substrate with chrome sublayer Ti-Cr electrode). The substrates were cut into pieces with size 1 × 2 cm. A chemically resistant varnish was applied to the back of the substrate and around the working area. The working area surface was about 1 cm2. A platinum mesh with size 3 × 3 cm was used as a counter electrode, and a silver chloride electrode (Ag/AgCl/3 M KCl) was used as a reference electrode.

The solution consisted of 0.015 M citric acid C6H8O7 (RusHim, 99.9%), indium chloride InCl3 (Sigma Aldrich, 98%), which concentration was varied in the range of 0.002–0.02 M, and deionized water. Citric acid is necessary to reduce the hydrolysis of indium cations. In addition, it contains complexing ligands. Deposition was performed at room temperature in galvanostatic mode at different current densities from − 0.1 to − 2 mA·cm−2 and in potentiostatic mode from − 0.8 to − 1.1 V for 5 min. Electrodeposition was carried out at room temperature (20 °C). The mode was set using an Autolab PGSTAT302N galvanostat/potentiostat. Currents are normalized to the geometric surface area of the electrode. Table 1 shows the pH values at different concentration of InCl3 in solution.

Table 1 The magnitude of pH from the concentration of InCl3 in solution \((C_{\mathrm{InCl}_3})\)
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The results of pH measurement showed that at these InCl3 concentrations, the dissociation of citric acid occurs predominantly in the first step:

$${H}_{3}{\text{Cit}}\leftrightarrow {H}_{2}{Cit}^{-}+{H}^{+}$$
(1)

Thus, some of the indium cations will form complex cations according to the reaction:

$${{\text{In}}}^{3+}+{{\text{H}}}_{2}{{\text{Cit}}}^{-}\leftrightarrow [{{\text{InH}}}_{2}{{\text{Cit}}]}^{2+}$$
(2)

Characterization methods

To estimate the efficiency of the electrochemical process (current efficiency η), the mass of the deposited In was compared with the theoretical. The theoretical mass was calculated according to Faraday’s law. The samples were weighed before and after deposition using the Mettler Toledo XP205 scale.

The morphology of the obtained samples was studied using scanning electron microscopy called a Zeiss Supra-40 microscope (Inlens SE detector was used, accelerating voltage = 10 kV, aperture = 30 μm). It was analyzed over an area of 50 µm2 using ImageJ software.

The pH values of the solution were measured using pH-meter HANNA HI 2002–02.

Results and discussion

It is known that the structure of the electrodeposited metal depends on the ratio of the rates of occurrence of crystallization centers and crystal growth; accordingly, it is this ratio that will determine the geometric characteristics of the formed array of In particles. In turn, this ratio depends on the parameters of the electrochemical process (potential, current density, concentration, etc.).

Cyclic voltammetry measurements were carried out to determine the values of the potentiostatic mode voltages of the studies. The cyclic voltammograms (CVs) of the sample were obtained at a sweep rate of 10 mV/s in solutions based on InCl3 with a concentration of 0.01 M and without InCl3 (Fig. 1). The plots were performed from OCP to negative potentials (− 1.7 V vs. Ag/AgCl), and then continued in the opposite direction towards to a more positive potential up to 0.6 V to end the test at the initial OCP potential value.

Fig. 1
figure 1

CVs obtained on Ti-Cr electrode in different solutions at a scan rate of 10 mV/s. Solution 1—0.015 M citric acid; solution 2—0.015 M citric acid + 0.01 M InCl3

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In the cathodic region, a slight increase in the cathodic current was observed in both solutions when the potential shifted towards more negative to − 1.0 V (plot A) (plot A for solutions 1 and 2 coincided). The literature analysis shows that mainly the reduction of indium-containing ions to metallic indium occurs in the range from − 0.6 V to − 0.8 V (vs. Ag/AgCl) depending on the process parameters (electrode material and solution composition) [23, 25,26,27,28,29,30]. However, in our case, only at a sufficiently negative potential (> − 1.0 V) a sharp increase in the cathodic current occurs. This change is due to the presence of a passive film on the chromium surface [31]. At potentials >  − 1.0 V, this film dissolves and reduction processes are observed, accompanied by a significant increase in cathodic current. In the case of solution 1, hydrogen is reduced (pH 2.58), and in the case of solution 2 (pH 2.3), hydrogen and indium are reduced. The mechanism of passive film dissolution (cathodic activation of chromium surface) is associated with the processes of hydrogen formation, its dissolution in the film, formation, and dissolution of chromium hydride [32]. During reverse scanning in solution 2, the so-called “nucleation loop” was observed on the CV. The higher value of the absolute value of the current density after reversal is associated with the change of the surface as a result of dissolution of the passive film and deposition of indium. In the anodic region of the voltammogram, when adding indium chloride to the citric acid solution, an anodic peak was observed (area D) associated with the oxidation of indium to indium-containing ions, with an almost finite zero current, indicating complete dissolution of the indium coating.

Chronoamperogram analysis was used to study the features of the indium nucleation mechanism. Based on CV (Fig. 1), several potential values for indium electrodeposition were selected. The current transients at different potentials of indium electrodeposition on a Ti-Cr substrate are shown in Fig. 2.

Fig. 2
figure 2

Current density transients obtained by electrodeposition of In particles in 0.01 M InCl3 + 0.015 M citric acid solution (pH 2.3) on Ti-Cr electrode at different potentials

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As one can see, at potentials of − 0.6 V and − 0.8 V, the current density remained almost constant during the whole process without reaching any maximum, which indicates the lack of indium nucleation on the substrate at these potentials. These potentials are insufficient to activate the surface of the chromium film. At more negative potentials of − 1 V and − 1.1 V, the current density increases and reaches the maximum value jm (mA·cm−2) at some time tm (s). After that the current density decreases and tends to the stationary value. An increase in current density is due to the nucleation and growth of indium nuclei. It is also worth noting the change in the increasing of current density (slope of the curve) at the initial stage, that is especially clearly visible at the potential of − 1 V (point A). The long time to reach the maximum current density is due to the cathodic activation time of the chromium film deposited on the titanium substrate. After activation, the increase in current density was due to the nucleation and growth of In nuclei.

The morphology of samples obtained at potentials of − 1 V and − 1.1 V during different deposition times is presented on the SEM images in Fig. 3. Thus, in Fig. 3a, d, the presence of In particles at this resolution of the microscope is not observed. This morphology was obtained 15 s after the start of particle deposition; it corresponds to the area of the current density increase (point A in Fig. 2).

Fig. 3
figure 3

SEM images of In particles obtained in 0.01 M InCl3 + 0.015 M citric acid solution (pH 2.3) on Ti-Cr electrode at − 1 V for 15 s (a), 60 s (b), and 300 s (c) and at − 1.1 V for 15 s (d), 60 s (e), and 300 s (f)

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The maximum current observed at high cathode potentials (Fig. 2) could be a result of particle growth overlap and/or diffusion zones, which subsequently affect the nucleation process of In. The inflection may indicate the completion of the nucleation process after 60 s of deposition (point B) when well-distinguishable particles with a size of 60–100 nm are formed (Fig. 3b, e and Table 2). In the process of establishing a stationary value of the current density (point C), the formed In particles increase in size, connect with each other, and form large clusters (Fig. 3c, f).

Table 2 Size analysis of In particles obtained in 0.01 M InCl3 + 0.015 M citric acid solution on Ti-Cr electrode at different potentials
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Theoretical and experimental studies of the formation of the crystalline phase have been investigated, starting with the early contributions of Fleischmann and Thirsk on determining the rate of nucleation of metals [33]. There are two-dimensional and three-dimensional processes of nucleation of metals. The three-dimensional models describe better the real processes during electrodeposition [34]. Then, these studies formed the basis for more complex models of nucleation. Important discoveries in this area were made by Scharifker and Hills, who proposed a model called the Scharifker–Hills (SH model) [35]. This model presents analytical equations for instantaneous and progressive three-dimensional nucleation, which are limited by diffusion. In this model, hemispherical nuclei are randomly situated on the surface of the electrode. Hemispherical diffusion zones for such nucleation center are independent of each other at the initial of the process and increase in such way that they overlap. In this case, the three-dimensional diffusion zones are replaced by planar zones, and the diffusion flux to single nucleus is described by a semi-infinite linear diffusion.

According to [35], the current density to the entire electrode is as follows:

$$j=\left(\frac{zF{D}^{1/2}c}{{\pi }^{1/2}{t}^{1/2}}\right)\left[1-{\text{exp}}(-N\pi kDt)\right],$$
(3)

where F is the Faraday’s constant (96,485 C/mol), c is the bulk concentration (mol/cm3), D is the diffusion coefficient (cm2/s), N is the number density of growing nuclei, and k is an empirical constant.

To determine the type of nucleation of the deposited indium particles, the current transients were transformed into (j/jm)2, and time axis was transformed into (t/tm). For each of the experimental curves, theoretical models were constructed in the same coordinates using Eq. 3 with numerical constants. Instantaneous nucleation was calculated by Eq. 4 with non-dimensional numerical values [35]:

$${(j/{j}_{m})}^{2}=\frac{1.9542}{(t/{t}_{m})}{(1-{\text{exp}}[-1.2564(t/{t}_{m})])}^{2},$$
(4)

and progressive was calculated by Eq. 5:

$${(j/{j}_{m})}^{2}=\frac{1.2254}{(t/{t}_{m})}{\left\{1-{\text{exp}}[-2.3367{(t/{t}_{m})}^{2}]\right\}}^{2}.$$
(5)

Based on the current transients shown in Fig. 2 and obtained at potentials − 1 V (jm =  − 1.46 mA·cm−2, tm = 62 s) and − 1.1 V (jm =  − 2.06 mA·cm−2, tm = 39 s), experimental data were compared with the theoretical models (Eqs. 4 and 5). The calculated dependencies are shown in Fig. 4.

Fig. 4
figure 4

Theoretical and experimental curves for electrodeposition In particles in 0.01 M InCl3 + 0.015 M citric acid solution (pH 2.3) on Ti-Cr electrode at different potentials

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In both cases of electrodeposition, the experimental curves coincide with the instantaneous type of nucleation. Thus, the nucleation of crystallization centers occurs very quickly over the surface of the substrate. After that, the formed particles (Fig. 3b, e) increase in size (Fig. 3c, f) without the generation of new ones during the further electrochemical process at t > tm.

In order to obtain more details on the nucleation process, the influence of an increase concentrations of InCl3 in the bath on the formation of arrays of In particles have been investigated. The following concentrations of InCl3 were selected: 0.002 M, 0.005 M, 0.01 M, and 0.02 M.

All current transients obtained at the potential of − 1.1 V are characterized by the increase of current density during 25–30 s of the process (Fig. 5), after which the density tends to the constant value. Also, the inflection on the current density curve becomes more visible at a higher concentration of InCl3. These current transients were plot in coordinates (j/jm)2 vs. (t/tm) (Table 3) using the SH model (Fig. 6).

Fig. 5
figure 5

Current density transients obtained by electrodeposition of In particles at different concentrations of InCl3 in 0.015 M citric acid solution at −1.1 V on Ti-Cr electrode

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Table 3 Values jm and tm for electrodeposition In particles at different concentrations of InCl3 in 0.015 M citric acid solution at − 1.1 V on Ti-Cr electrode
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Fig. 6
figure 6

Theoretical and experimental curves for electrodeposition of In particles obtained at − 1.1 V from 0.015 M citric acid solutions with different concentrations of InCl3

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At the low concentrations of InCl3 (0.002 M and 0.005 M), the experimental curves are close to the theoretical curves of instantaneous nucleation at t < tm (Fig. 6). However, the obtained experimental dependences do not go well with the theoretical curves of instantaneous or progressive nucleation at t > tm. This can be explained by the influence of additional reactions that can make a considerable impact exactly at this potential during the indium-containing ions reduction process on the electrode. Therefore, in this case, the reaction can be limited by the kinetics of the electrochemical reduction reaction of the indium-containing ions, so the SH model does not correctly enough describe such case of nucleation. This suggests the necessity to introduce additional coefficients in Eq. 3 for the SH model but there are no systematic models for estimating metal nucleation that take into account several reactions in the electrodeposition process [30, 36].

The conclusion about the effect of additional reactions during In electrodeposition is confirmed by calculating the efficiency of the indium-containing reduction (current efficiency η) on the electrode (Table 4). To estimate the efficiency of the electrochemical process (current efficiency η), the mass of the deposited In was compared with the theoretical. The theoretical mass was calculated according to Faraday’s law.

Table 4 Current efficiency of In electrodeposition at − 1.1 V for 5 min from 0.015 M citric acid solutions with different concentrations of InCl3
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With an increase of InCl3 concentration in the electrolyte from 0.002 to 0.02 M, the current efficiency accordingly increases from 38 to 83%. Therefore, due to the relatively low deposition efficiency of In at concentrations of 0.002 M and 0.005 M, separate spherical particles of In are still present after 5 min of the process (Fig. 7a, b) with average sizes of 90 nm and 260 nm (Table 5). At concentrations of 0.01 M and 0.02 M, another nucleation mechanism operates. At these concentrations almost during the whole deposition time, the instantaneous type of nucleation is observed (Fig. 6c, d). This leads to the rapid growth of the particles and the formation of indium clusters that is the cause of film formation (Fig. 7c, d) after deposition during 5 min.

Fig. 7
figure 7

SEM images of In particles obtained at − 1.1 V for 5 min from 0.015 M citric acid solutions with different concentrations of InCl3: 0.002 M (a), 0.005 M (b), 0.01 M (c), and 0.02 M (d)

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Table 5 Size analysis of In particles obtained at − 1.1 V for 5 min from solutions with different concentrations of InCl3
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Further studies were carried out at different current densities. The values of the current densities were chosen based on the CVs (Fig. 1). Galvanostatic deposition of In particles occurred at the following current densities: − 0.1 mA·cm−2, − 0.5 mA·cm−2, − 1 mA·cm−2, and − 2 mA·cm−2. The obtained curves in such modes are shown in Fig. 8.

Fig. 8
figure 8

E–t curves obtained by electrodeposition of In particles in 0.01 M InCl3 + 0.015 M citric acid solution (pH 2.3) on Ti-Cr electrode at various current density

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All cases are characterized by the sharp increase of potential during the first seconds of the process. At the same time, at low current density (− 0.1 mA·cm−2), the increase stage of the potential curve occurs within 30 s, while at higher current densities, this process takes only 2 s. This may indicate the incompleteness of the particle nucleation stage at low current density. After the inflection, the potential values at the modes − 0.1 mA·cm−2, − 0.5 mA·cm−2, and − 1 mA·cm−2 tend to the stationary value (− 0.75 V, − 0.8 V, and − 0.91 V), and at current density of − 2 mA·cm−2, the potential value rises to − 1.25 V.

For the galvanostatic formation of metal particles, it is not typical to investigate the nucleation mechanism like in the potentiostatic mode using the SH model. Although there are some articles where the research of the growth of nuclei formation occurs with using the chronopotentiometry method and the SH model [37], in our case, such analysis is incorrect due to the strong discrepancy between experimental and theoretical curves. Thus, this issue requires additional research because there are very few studies of the mechanism of nucleation of particles using chronopotentiometry.

Figure 9 shows SEM images of In particles obtained at current densities in the range from − 0.1 to − 2 mA·cm−2 for 5 min (the InCl3 concentration was 0.01 M).

Fig. 9
figure 9

SEM images of In particles obtained from 0.01 M InCl3 + 0.015 M citric acid solution (pH 2.3) for 5 min at various current density: − 0.1 mA·cm−2 (a), − 0.5 mA·cm−2 (b), − 1 mA·cm−2 (c), and − 2 mA·cm.−2 (d)

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At a low current density of − 0.1 mA·cm−2 (at which the potential is set to be more positive than the potential at point A in Fig. 1, corresponding to the beginning of an increase in the cathode current), indium particles are not observed (Fig. 9a). Even an increase in the duration of the process compared to other samples (10 min) does not allow the formation of full-fledged indium particles at such a current density. The data obtained confirm that at potentials more positive than − 0.8 V, electrochemical deposition of indium does not occur. With an increase in current density to − 0.5 mA·cm−2 (when the potential is set to be more negative than the potential of point A in Fig. 1), separate rarefied large particles of indium appear (Fig. 9b) with sizes up to 0.5–1 μm, also one can observe the faceting of the crystal along certain crystallographic planes. In addition, there are particles strongly elongated up to 2 μm in one direction. A change in particle morphology occurs at higher current densities (− 1 mA·cm−2), in which case the particles are located close to each other (Fig. 9c). The characteristic size for particles obtained at − 1 mA·cm−2 is about 300 nm. At − 2 mA·cm−2, adjacent indium particles grow together and large clusters are formed (Fig. 9d).

Another important parameter that can affect the geometric characteristics of the resulting particles is the InCl3 concentration in the solution. The kinetics obtained at the current density of − 1 mA·cm−2 with concentrations InCl3 from 0.002 to 0.02 M in electrolyte solutions are shown in Fig. 10. The type of the obtained dependences is similar to those presented earlier at different current densities (Fig. 8). For all cases of concentration changes, in the initial stage of electrodeposition process (within a few seconds), the increase in potential to − 1.1 V for 0.01 M and 0.02 M InCl3 and to − 1.2 V for 0.002 M and 0.005 M InCl3 is observed. Then, the potential values almost reach the stationary values after inflections.

Fig. 10
figure 10

E–t curves obtained by electrodeposition of In particles in 0.01 M InCl3 + 0.015 M citric acid solution (pH 2.3) at − 1 mA·cm−2 and various InCl3 concentration on Ti-Cr electrode

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Figure 11 shows SEM images of the morphology of indium particles obtained from 0.015 M citric acid solutions with different concentrations of InCl3 (from 0.002 to 0.02 M) at a current density of − 1 mA·cm−2 for 5 min.

Fig. 11
figure 11

SEM images of In particles obtained at − 1 mA·cm.−2 for 5 min from + 0.015 M citric acid solutions with different concentrations of InCl3: 0.002 M (a), 0.005 M (b), 0.01 M (c), and 0.02 M (d)

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The results of indium particle size analysis are shown in Table 6. At the initial stages of increasing the concentration of InCl3 in solution (0.002 M and 0.005 M), there is a linear change in the main geometric characteristics of the particles (Fig. 11a, b) and a unimodal nature of the particle size distribution (inserts in Fig. 11a, b). The average size and dispersion increased from 70 to 150 nm and from 150 to 300 nm, respectively, while the density of particles naturally decreased by approximately two times (from 73·108 to 31·108 cm−2).

Table 6 Size analysis of In particles obtained at − 1 mA·cm−2 for 5 min from solution with different concentrations of InCl3
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With an increase in the concentration of InCl3 in the solution, changes in the resulting morphology appear (Fig. 11c, d). Thus, at a concentration of 0.02 M compared to 0.01 M, the density of particles decreases from 7·108 to 1·108 cm−2, which, with an approximately equal average particle size of 360 and 540 nm, respectively, leads to a greater sparsity in the arrangement of particles at a concentration of 0.02 M. At the same concentration, large particles of complex shape appear, the sizes of which reach up to 0.5–2 microns in one direction, formed as a result of the intergrowth of neighboring particles, which is not typical for the results obtained at lower concentrations of indium.

In general, with a change in the InCl3 concentration, an almost linear increase in the average size of indium particles is observed; the density of particles on the surface decreases exponentially (Fig. 12).

Fig. 12
figure 12

The average In particle size o and their surface density depending on the concentration of InCl3 in solution at − 1 mA·cm.−2

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Conclusions

In this work, the dependence of the morphology and geometric characteristics of the obtained indium particles on the parameters of the electrodeposition process is shown. During the experiments, it was found out that the nucleation of In particles at the potential higher than − 1 V does not occur. The process of In nucleation was also analyzed depending on the applied voltage and the concentration of InCl3 in the solution using the SH model. At potentials − 1 V and − 1.1 V with InCl3 concentration of 0.01 M, the nucleation mechanism corresponded to the instantaneous type.

When analyzing the type of nucleation of In particles, depending on the concentration of InCl3, it was found that at a concentration of 0.002 M and 0.005 M, the experimental curve did not correspond to the instantaneous or progressive type of nucleation at t > tm, which may be associated with additional reactions except In reduction. At the same time, at 0.01 M and 0.02 M of InCl3, the experimental curves coincided with the instantaneous type of nucleation. The effect of additional reactions during electrodeposition of In is confirmed by the low current efficiency (38%) with a gradual increase to 83% with the increase in the concentration of InCl3.

In galvanostatic mode of In electrodeposition, it has been established that, with an increase in the InCl3 concentration in solution from 0.002 to 0.02 M, the average particle size increases almost linearly, while their number per unit area decreases exponentially.

The results obtained in this work will be useful in the formation of arrays of In particles with specified sizes for use in various devices based on them.