KR20190088267A - Manufacturing method of nanomaterial with controlled shape and size - Google Patents

Abstract

The present invention relates to a manufacturing method for a nanomaterial catalyst with an adjustable shape and size. The present invention relates to a technique of metalizing the surface of a carbon material with nickel by using an atomic layer deposition method and using the metalized carbon material as a catalyst. According to the present invention, the shape and size of the nickel metalized on the surface of the carbon material by the atomic layer deposition method using NH_3 gas or NH_3 plasma can be controlled. Moreover, the carbon material can maximize the surface area of the nickel metalized on the surface. So, the carbon material has a remarkable effect to improve performance when being applied as the catalyst or an electrode material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a nanomaterial,

The present invention relates to a method of fabricating a nanomaterial capable of adjusting shape and size, and relates to a technique for depositing nickel on the surface of a carbon material by atomic layer deposition and applying it to a catalyst and an electrode material.

Nickel (Ni) is one of the most widely used metals and has applications in both microscale and nanoscale. For example, there are applications for alloy parts, magnetic recording media and battery electrodes, semiconductor device welding points, and fuel cell catalysts. Because many practical applications of Ni utilize their surface properties, a thin-film nickel coating to achieve a higher surface-to-volume ratio than is possible in bulk materials may be advantageous in reducing manufacturing costs.

Atomic layer deposition (ALD) is a useful method for uniformly coating nanoscale 3D structures with precise thickness control. So far, several studies have been conducted using Ni precursors and counteractants. However, most of the previous studies on ALD Ni have focused on several applications such as semiconductor devices and magnetic media, so only limited substrate types such as Si, SiO ₂ , and Al ₂ O ₃ have been studied. Since ALD is based on sequential surface reactions, the growth characteristics during ALD are highly dependent on the substrate (Patent Document 1). Therefore, understanding of ALD Ni on various substrates should be able to expand applications.

Carbon surfaces are very important for many applications. For example, porous carbon is the most widely used electrode and catalyst support material because it can be easily fabricated with a high surface area structure. In addition, the carbon support is chemically inert in both acidic and basic media and prevents undesirable side reactions in the catalytic process. In addition, ALD is an effective deposition method for forming catalysts within complex carbon structures because it provides superior uniformity compared to other deposition methods.

Despite the potential benefits of the aforementioned applications, however, a similar study of ALD Ni on carbon surfaces has not yet been conducted.

Accordingly, in the present invention, the ALD deposition method on the surface of the carbon material stably deposits nickel, and further, a method of controlling the shape and size of the deposited nickel.

Korean Patent No. 1581613

It is an object of the present invention to stably deposit nickel on the surface of a carbon material by atomic layer deposition, and to provide a manufacturing method capable of controlling the shape and size of the deposited nickel.

In addition, the carbon material on which nickel is deposited is intended to be used as a catalyst and an electrode material as a nano material.

According to a representative aspect of the present invention, there is provided a method of manufacturing a nano material including depositing nickel on the surface of a carbon material by atomic layer deposition,

(a) an exposure step of adsorbing a nickel precursor on a surface of a carbon material to adsorb it;

(b) purging the unadsorbed nickel precursor;

(c) reacting the nickel precursor adsorbed carbon material with the reactants; And

(d) a final purging step of removing remaining unreacted material after completion of the reaction,

Wherein the reactant is NH ₃ gas or NH ₃ plasma.

The NH ₃ gas is preferably injected at a temperature of 50 to 100 ° C at a flow rate of 100 to 400 sccm for 5 to 10 seconds.

The NH ₃ plasma is preferably performed by applying a power of 100 to 400 W for 5 to 10 seconds.

In the step (a), the carbon precursor is pre-treated with a reactant before the nickel precursor is introduced.

The nickel deposited on the surface of the carbon material is preferably formed of nanowires or nanofilms.

The nanowire is preferably formed along the step edge of the carbon material surface.

In the above production method, it is preferable that the cycle consisting of steps (a) to (d) is repeatedly performed.

As the number of cycles increases, the length of the nanowires deposited on the carbon surface increases, or the thickness of the nanofilm increases.

Preferably, the carbon material is graphite and the nickel precursor is Nickel (dmamb) ₂ . In the present invention, dmamb means 1-dimethylamino-2-methyl-2-butanolate.

According to another exemplary aspect of the present invention, there is provided a catalyst or an electrode comprising a Naso material produced by the method.

According to the present invention, the shape and size of the nickel deposited on the surface of the carbon material can be controlled through atomic layer deposition using NH ₃ gas or NH ₃ plasma.

Furthermore, the carbon material can maximize the surface area of the nickel deposited on the surface, and has a remarkable effect in improving the performance when applied as a catalyst or electrode material.

1 (a) to 1 (d) show AFM (atomic force microscopy) images of Ni formed on HOPG (Highly ordered pyrolytic graphite) deposited by thermal ALD as the number of ALD (Atomic layer deposition) cycles increases (e) are graphs showing the lengths of the Ni nanowires formed on the HOPG and the thickness of the Ni film formed on the SiO ₂ according to the number of ALD cycles.
2 (a) - (d) are X-ray photoelectron spectroscopy (XPS) spectra of H 1 O, N 1 s and C 1 s regions of HOPG exposed to NH ₃ gas for various periods, ₃ is a graph showing the relative amount to the functional group formed on the HOPG as a function of the exposure time (tNH ₃ , _g ), and (f) shows the width of the Ni nanowire as tNH ₃ , _g .
3 (a) and 3 (b) are images showing a planar SEM (Scanning Electron Microscopy) image of Ni-deposited PE-ALD using NH ₃ plasma and deposition for 100 and 500 cycles on HOPG.
4 (a) is an AFM image showing the surface of HOPG immediately after exposure to NH ₃ plasma for 5 minutes, (b) and (c) are graphs showing XPS spectrum results, (d) Lt; / RTI > is the graph showing the DFT calculated adsorption energies (Eads) of Ni precursor during formation.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

According to an aspect of the present invention, there is provided a method of manufacturing a nano material including depositing nickel on a surface of a carbon material by atomic layer deposition,

(a) an exposure step of adsorbing a nickel precursor on a surface of a carbon material to adsorb it;

(b) purging the unadsorbed nickel precursor;

(c) reacting the nickel precursor adsorbed carbon material with the reactants; And

(d) a final purging step of removing remaining unreacted material after completion of the reaction,

Wherein the reactant is NH ₃ gas or NH ₃ plasma.

The carbon material is the most widely used electrode and catalyst support material because it can be easily produced with a high surface area structure such as porous carbon. In particular, when used as a catalyst support, it is chemically inert in both acidic and basic media and can prevent undesirable side reactions in the catalytic process.

In the present invention, highly ordered pyrolytic graphite (HOPG) is used as a catalyst and an electrode material among carbon materials.

According to the present invention, the nickel (Ni) is deposited on the surface of the carbon material at a nanoscale, and is deposited in the form of nanowires or nanofilms having a high surface-to-volume ratio through atomic layer deposition, The present invention has a remarkable effect in improving the performance of the device.

Atomic layer deposition (ALD) used in the present invention is a technique capable of depositing a substance to be adsorbed on the surface of a substrate by nanoscale thin film deposition through chemical adsorption and desorption reaction.

According to the present invention, nickel can be deposited on the surface of the carbon material through the atomic layer deposition method, and the shape and size of the deposited nickel can be controlled by a simple method of controlling the counteractant (hereinafter, 'reactant').

A method for producing the nanomaterial will be described in detail as follows.

First, in the step (a), a nickel precursor is put on a surface of a carbon material and is adsorbed.

Before performing the step (a), the carbon substrate was cleaned by removing the layer exposed on the surface by attaching and peeling the tape before putting it into the process chamber without a separate cleaning process. Then, a nickel precursor was added thereto together with argon gas for adsorption. At this time, in order to obtain a proper vapor pressure of the nickel precursor, the bubbler containing the precursor was heated to 60 to 80 캜.

Preferably, the carbon precursor is pre-treated with a reactant (NH ₃ gas or NH ₃ plasma) before the nickel precursor is introduced. This When pre-treated with the NH ₃ gas, and improve the selectivity to the chemical adsorption of a Ni precursor, said lead did induce growth of the nanowires, when the pre-processing to the NH ₃ plasma is evenly Ni on the entire surface of the carbon material deposited It was a role to play.

The step (b) is a purging step of reacting the carbon precursor with the carbon precursor through the step (a), and then removing the unadsorbed nickel precursor through the reaction.

The purging was performed by flowing an inert gas such as argon to remove the unadsorbed nickel precursor.

In the step (c), the carbon precursor-adsorbed carbon material is reacted with the reactant through the step (b).

In the step (c), the carbon material is exposed to the reactants to reduce the adsorbed nickel precursor and produce by-products.

According to the present invention, it is possible to control the morphology of the finally adsorbed nickel by performing the reactants differently.

That is, according to an embodiment of the present invention, the NH ₃ gas may be used as the reactant to deposit nickel in nanowire form.

At this time, the NH ₃ gas 50 to a temperature of 100 ℃ it is preferred that the injection for 5 to 10 seconds at a flow rate of 100 to 400 sccm, a range of the temperature and the flow rate can be uniformly reacting the NH ₃ gas to the sample Not desirable.

According to another embodiment of the present invention, NH ₃ plasma treatment may be performed on the reactants to deposit nickel in the form of nanofilms.

The NH ₃ plasma is preferably performed by applying a power of 100 to 400 W for 5 to 10 seconds. If it is out of the above range, the sample due to the radical of the plasma may be seriously damaged, which is not preferable.

That is, the shape of the nickel formed on the surface of the carbon material can be deposited as nanowires or nanofilms by controlling the shape of the reactants. The control of such a deposition material is possible when highly ordered pyrolytic graphite is used as the carbon material and nickel is used as the deposition material. When the above-mentioned carbon material is used or a substrate of a material other than carbon is used It was confirmed that the shape and size of the nickel were not controlled.

The step (d) is a final purging step of removing remaining unreacted material after completion of the reaction of step (c).

In step (d), an inert gas such as argon gas was used to remove unreacted materials. The flow rate and exposure time were maintained in the same conditions as in step (b).

According to the present invention, in the method of manufacturing a nanomaterial, the cycle consisting of the steps (a) to (d) may be repeatedly performed.

When NH ₃ gas is used as the reactant, the cycle is preferably performed in 1 to 200 cycles. The cycle can increase the number of times the length of the nickel nanowire deposited on the carbon material surface increases, and the nanowire is formed along the step edge of the carbon material surface.

If the cycle exceeds 200 cycles, the rate of increase of the length of the Ni nanowires is rather reduced, which is not preferable.

When the NH ₃ plasma is used as the reactant, the cycle is preferably performed in 1 to 500 cycles. The number of cycles may be increased to increase the thickness of the nickel film.

Particularly, although not explicitly described in the following examples or comparative examples, in the method for producing a nano material according to the present invention, it is preferable that the kind of the nickel precursor and the carbon material, the pretreatment conditions of the nickel precursor and the carbon material Was used for the electrodes, and the durability of the electrode was confirmed after 300 times of using.

As a result, unlike the case where experiments were conducted under different conditions and different numerical ranges, (i) the nickel precursor uses Ni (dmamb) ₂ , (ii) the carbon material uses graphite, (iii) The nickel precursor is pre-treated with a reactant (NH ₃ gas or NH ₃ plasma) before being reacted with the carbon material, and (iv) the nickel precursor is transferred to the reactor in an argon atmosphere, , It was confirmed that not only the internal step edge which is a step edge in which the chemical reactivity is reduced does not occur in Ni but also maintains initial performance in durability even when used up to 300 times .

On the other hand, if any one of the conditions (i) to (iv) is not satisfied, the internal step edge is rapidly generated in the Ni formed on the surface of the carbon material in the nanomaterial, It was confirmed that the performance was deteriorated sharply than the initial performance.

According to another aspect of the present invention, there is provided a catalyst or an electrode material including a nanomaterial manufactured according to the method for manufacturing a nanomaterial.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope and content of the present invention can not be construed to be limited or limited by the following Examples. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the present invention as set forth in the following claims. It is natural that it belongs to the claims.

In addition, the experimental results presented below only show representative experimental results of the embodiments and the comparative examples, and the respective effects of various embodiments of the present invention which are not explicitly described below will be specifically described in the corresponding part.

Example

A commercial double-showerhead type ALD chamber (CN-1, Atomic premium) equipped with a rod-lock (a way of inserting and removing samples without breaking the vacuum of the entire vacuum system) was used for ALD Ni. The radio frequency plasma generator is connected to the showerhead and the ground stage. The chamber configuration is described in 'Yoon J, Song J-G, Kim H and Lee H. 2015 Plasmaenhanced atomic layer deposition of Co on metal surfaces Surf. Coat. Technol. 264 60-5 '.

Ni (dmamb) ₂ (dmamb = 1-dimethylamino-2-methyl-2-butanolate) was used as the nickel precursor and NH ₃ was used as the counteractant. The nickel precursor contained a glass bubbler to maintain the temperature at 70 [deg.] C to create the proper vapor pressure. The evaporated Ni (dmamb) ₂ (dmamb = 1-dimethylamino-2-methyl-2-butanolate) was transferred to the main chamber under an argon gas atmosphere. The argon gas was used for over-reaction and precursor injection and by-product purification during the NH ₃ exposure step. The NH ₃ gas was introduced into the chamber at a flow rate of 400 sccm. Plasma enhanced ALD (plasma-enhanced atomic layer deposition, PE-ALD), plasma was generated between the substrate and the showerhead while the NH ₃ was exposed to 300 W of power. A single ALD cycle consists of precursor exposure, purging, reactant exposure and final purging with a duration of 10 s, 5 s, 10 s and 5 s.

The substrate temperature was maintained at 300 占 폚. Ni was deposited on SiO ₂ and HOPG substrates (size: 10 mm x 10 mm, ZYB quality, K-TEK Nanotechnology). The surface of HOPG (Highly oredred pyrolytic graphite) was cleaned by stripping the surface graphite using a well-known method of scotch tape to obtain a fresh graphene layer from graphite ('Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, Grigorieva IV and Firsov AA 2004 Electric field effect in atomically thin carbon films Science 306 666-9). HOPG was loaded into the chamber as soon as a clean surface was ready. The SiO ₂ substrate was immersed in acetone, IPA and deionized water, washed, and dried by blowing N ₂ .

Before the thermal ALD process by Ni NH ₃ gas and the NH ₃ plasma to study the effects of NH ₃ for the ALD process were carried out pre-processing of the HOPG substrate. Pretreatment and ALD processes were performed in the same chamber under constant vacuum conditions. Field emission scanning electron microscopy (FE-SEM) and AFM of the tapping mode were used to analyze the morphology of the HOPG surface including ALD Ni. The length of Ni nanowires was obtained by direct measurement of 30 points from AFM images using the image processing program (XEI). Chemical binding of the material was analyzed by XPS. The hardness of the ALD Ni film and the adhesion between the Ni and the SiO ₂ substrate were measured by ASTM D3363 pencil test and ASTM D3359 tape test. The ALD Ni film was cut with a sharp knife along a guide line spaced at 1 mm intervals. A commercially available 3M (No.550R) tape was firmly attached to the surface and rubbed with an eraser. The tape was quickly removed back. A 30 nm thick ALD Ni on a SiO ₂ substrate was used for pencil hardness testing. For pencil testing, a 7H pencil (Mitsubishi pencil) was attached to the surface of the sample and monitored for scratch formation.

The density function theory (DFT) was calculated using Orca version 3.0.3. A well-performed dispersion-corrected PBE0-D3 function for the molecular Ni catalyst was used with the def2-SVP base set and the RIJCOSX approximation. The basal plane of HOPG was modeled as a C ₃₇ H ₁₆ cluster with H-terminated edges, similar to the clusters previously used in the investigation of ALD Pt on graphene. Surface nitrogen species including graphite N and amino groups were also considered at the center of the cluster. The Ni precursor was assumed to be initially physisorbed on the surface during the pulse as follows:

cluster + precursor → (full precursor adsorbate) (1)

The NH ₃ proton as a counteractant and the substrate are ligands of the adsorbed precursor according to the following stepwise reactions (2) and (3).

(full precursor adsorbate) + 2NH ₃ ? (-1L adsorbate) + LH? (2)

(-1 L adsorbate) + 2 NH _{3 -} (-2 L adsorbate) + LH ↑ (3)

Here, LH means 1-dimethylamino-2-methyl-2-butanol. The adsorption energy (Eads) of the surface Ni species is defined as the difference between the electrical energy of the reactants and the product, and can be expressed by the following equation (4).

(Eads = Σ [E (adsorbate ) + αE (LH)] - Σ [E (cluster) + E (precursor) + bE (NH 3)] (4)

Where a and b are the coefficients of each chemical equation

Experimental Example 1: Analysis of Ni formed on HOPG according to the number of ALD cycles

Figures 1 (a) - (d) show AFM images of Ni formed on HOPG deposited by thermal ALD as the number of ALD cycles increases. Figure 1 (a) shows the atomic step and flat surface of the basal plane of the HOPG with the edges deposited by Ni particles after ALD. In FIGS. 1 (b) to (d), as the ALD cycle continues, the particles are connected and consequently form a nanowire shape. As a result, it can be seen that the width of the generated Ni nanowires is increased rather than the particles are formed in the basal plane region where no nanowires are formed in the previous cycle. This growth behavior of ALD Ni on HOPG was observed similar to ALD Pt on HOPG. In this case, because the step edge is more chemically reactive than the basal plane, Pt forms nuclei predominantly at the step edge. The selective formation of ALD Ni on HOPG can be expected due to the same reason. Also, in Fig. 1 (a), there are several step edges in which nuclei of Ni are not generated and remain as they are. This can be explained by the presence of an internal step edge whose chemical reactivity is reduced due to the presence of another graphite sheet on top of it, although the shape is similar to that of an external step edge with higher reactivity.

FIG. 1 (e) shows the Ni nanowire length formed on the HOPE and the thickness of the Ni film formed on SiO ₂ according to the number of ALD cycles. In the case of Ni thin films formed on SiO ₂ , the thickness increases as the number of ALD cycles increases. According to a previously published study, the growth rate measured on SiO ₂ is 0.63 Å / cycle. There are two different reasons for the observed increase in length of nanowires on HOPG. The Ni nanowire length increase rate up to 200 cycles is 2.07 Å / cycle and decreases to 0.79 Å / cycle after 200 cycles. If the growth of ALD Ni on HOPG is isotropic in the transverse and longitudinal directions, the nanowire length growth rate would be 1.26 A / cycle, twice the vertical growth rate of 0.63 A / cycle. During the initial growth period, the length growth rate of the Ni nanowires is higher than the isotropic growth rate and becomes smaller after 200 cycles. This difference will be explained by the various wettability of the metal on the HOPG.

The contact angle (CA) of the metal on the HOPG can be determined from the ratio of the width and height of the particles on the surface (g _w / 2g _t ). That is, as shown in FIG. 1 (e), g _w / 2 g _t of the Ni nanowire The values are 1.643 and 0.627, respectively, corresponding to = 62.6 ° and = 115.5 °. This contact angle value indicates that the Ni nuclei wet the HOPG surface relatively well during the initial growth, but then the wettability decreases at the growth stage. This phenomenon is explained by Fig. 1 (e). The initial contact angle of ALD Ni is 62.6 °, which is smaller than ALD Pt 75 °. Generally, for liquid substances, the contact angle is determined by the interaction between the three components of matter, substrate and vapor. If the surface energy of the material is high, the contact angle is higher due to the large cohesion within the material. The various literature values for the surface energies of the (111), (110) and (100) planes of Pt and Ni are determined by experimental and theoretical methods. As a result of analysis of this data, the surface energies of some major Ni crystal planes were 2.426 Jm ^{-2 on the} (100) plane and 2.011 Jm ^-2 on the (110) plane, (111) plane is smaller than the mean value of 2,799 Jm ^-2 , (110) plane is 2.819 Jm ^-2 , and (111) plane is 2.299 Jm ^-2 . Therefore, when the contact angle of the Ni nanowires is smaller than the contact angle of the Pt nanowires, the surface energy of the Ni decreases. Interestingly, the contact angle of the Ni nanowires was observed to increase to over 200 ALD cycles.

At the same time as the lateral growth rate changed, the vertical growth rate of ALD Ni on HOPG (as determined from AFM data) also increased slightly. This may be due to one of two factors. First, the ALD reaction leading to Ni deposition is dominant in the vertical direction than in the transverse direction. The second is that even though the vertical and lateral growth rates of Ni do not change at the initial growth stage, they seem to change due to the adhesion and coarsening of Ni nuclei. Since the chemical reactivity of ALD Ni has no directional dependence, it is possible that the growth rate change over 200 cycles is due to the latter reason. In Ni film, an abnormally fast aggregation phenomenon and a coarsening phenomena (a phenomenon in which a crystal grain becomes larger as a polycrystal is heated to a high temperature) occurs. This indicates that Ni films on amorphous carbon have relatively fast migration and crystal grain coarsening when annealed at 623 K for 6 hours, which was an observation that can not be explained by conventional atomic models. Based on this, the rapid growth rate of less than 200 cycles of Ni nanowires grown on HOPG can be understood by considering that the step edge of HOPG is similar to the surface of amorphous carbon, and the deposition temperature of 300 ° C is the annealing temperature It is similar to temperature.

Experimental Example 2: Effect of NH on HOPG surface ₃  Gas impact analysis

To analyze the effect of NH ₃ gas on HOPG surface during Ni ALD, HOPG was exposed to NH ₃ gas prior to Ni ALD. (A) to (d) of Figure 2 shows the XPS spectra from the O1s, N1s and C1s region of the HOPG exposed to the NH ₃ gas for various lengths of time.

Referring to FIG. 2, no N was observed even after NH ₃ gas exposure, as shown in the XPS results of FIG. 2 (a). The O1s peak of HOPG before Ni ALD treatment was detected at about 532.6 eV with a shoulder peak of 534 eV and a tail of 530.9 eV as shown in Fig. 2 (b). O 1s peaks appear in a variety of ways such as -OH, O = C-OH, and CO, which are also observed in the 1s region of carbon (FIGS. 2c and 2d). This type of oxygenated species appears to originate from a step edge with a dangling bond rather than a basal plane.

As shown in FIG. 2 (b), it can be seen that even when the NH ₃ gas is exposed to the NH ₃ gas for 60 minutes, the composition of the O species does not change.

Figure 2 (e) shows the relative amount to the functional groups formed on HOPG as a function of exposure time (NH ₃ , _g ) of NH ₃ . And substantially constant at the step edge to the relative amount of the NH ₃ NH ₃ for 60 minutes for each species, which indicates the tNH _{3, g} does not significantly change the HOPG surface.

2 (f) shows the width of the Ni nanowire as tNH ₃ , _g . According to FIG. 2 (f), Ni nanowires deposited on HOPG without pretreatment show a length of 26.42 nm, again indicating that NH ₃ gas pretreatment does not significantly change the HOPG surface, and tNH ₃ , _g The value is constant up to 60 minutes. This is because NH ₃ removes the function from the carbon surface due to the reducing power. Similarly, it is meant that the NH ₃ gas suppresses the oxidation of HOPG, thereby improving the selectivity for the chemical adsorption of the Ni precursor of the step edge and inducing the growth of Ni nanowires. Even if the NH ₃ gas reduces the carbon surface, the bond between C and O shown in FIGS. 2 (b) to 2 (d) can still be detected. This is because HOPG can be oxidized by exposure to air when transferring samples from ALD to XPS. The formation of oxygen-related species on a fresh carbon surface by atmospheric exposure is a well-known phenomenon. Therefore, the XPS spectrum of the carbon surface after atmospheric exposure can show oxidation even after reduction with NH ₃ gas in the ALD chamber.

Experimental Example 3: Preparation of NH ₃  Analysis of Ni Growth Behavior on HOPG Surface by Plasma

Since plasma has higher reactivity than gas, different growth behavior of ALD Ni on HOPG can be expected when NH ₃ plasma is used.

3 (a) and 3 (b) are images showing a planar SEM image of Ni-deposited PE-ALD using NH ₃ plasma and deposited for 100 and 500 cycles on HOPG. In contrast to Ni deposited by thermal ALD using NH ₃ gas, both SEM images clearly show that Ni was uniformly deposited on the entire surface of the HOPG.

In a further experiment, thermal ALD of Ni was performed after pretreatment of HOPG surface with NH ₃ plasma for 5 minutes. A planar image of this sample is shown in Figure 3 (c). Interestingly, no deposition selectivity was observed with the thermal ALD of Ni using NH ₃ gas after NH ₃ plasma pretreatment, and the type of Ni in FIG. 3 (c) was almost the same as Ni in FIG. 3 (b). These results indicate that NH ₃ plasma activates the surface of HOPG with thermal ALD of Ni. NH ₃ plasma forms various atomic and molecular radicals such as H, N, NH and NH ₂ adsorbed on the graphene sheet to destroy the sp2 carbon skeleton.

Thus, defects introduced by NH ₃ plasma on the basal plane can be expected to act as nucleation sites on the HOPG to enhance nucleation of Ni.

Experimental Example 4: Effect of NH on the substrate ₃  Analysis of influence of plasma

In order to clarify the effect of NH ₃ plasma on the substrate, the morphology and chemical state of HOPG surface after NH ₃ plasma treatment were analyzed by AFM and XPS.

4 (a) is an AFM image showing the HOPG surface immediately after exposure to NH ₃ plasma for 5 minutes. Referring to FIG. 4 (a), it can be seen that the surface of the HOPG is rough and the rugged shape is formed entirely of the surface. The surface roughness of the NH ₃ - plasma - pretreated HOPG was 1.44 Å in the red square, and the basal plane of the fresh HOPG as a control group showed a roughness of 0.74 Å in the AFM apparatus.

According to the XPS spectra of FIGS. 4 (b) and 4 (c), the C 1s and N 1s regions are formed by NH ₃ plasma of surface nitrogen species such as N, amine, pyridine N and imine of graphite on the HOPG surface Integration. Therefore, surface nitrogen species introduced by NH ₃ plasma can act as nucleation sites for the deposition of Ni during thermal ALD or PE-ALD. It should be noted that oxidized functionality, such as imide and amide, may result from air contamination that occurs during the experiment.

Figure 4 (d) shows the DFT calculated adsorption energies (Eads) of the Ni precursor during the initial nucleation of the graphite surface, with or without surface nitrogen species. It has been observed that the formation of the same type of adsorbate is consistently preferred on the initial surface or on amino-functionalized surfaces than graphite N in the Eads's view. This stabilization provided by the amino group is probably due to the ability of the amino group to transfer hydrogen bonds to the nickel adsorbate. The difference in energy between the basal plane and the amino-functionalized surface is as large as 11.6 to 13.2 kcal mol ^{-1 due} to the elimination of both ligands. At an ALD process temperature of 300 ° C, this difference in Eads may be greater than four times the likelihood of occupation of the amino defects rather than the location of the basal plane. On the other hand, if a hydrogen bonding complex is formed on the surface, the activation barrier for NH ₃ dissociation adsorption is significantly lowered, and thus the amino functional group can accelerate the deposition reaction rate compared to NH ₃ dissociation adsorption. Therefore, introduction of amino defects on the graphite surface by NH ₃ plasma can improve nucleation of ALD Ni.

Therefore, as a result of forming ALD Ni on HOPG using NH ₃ in gas and plasma state as a counteractant, in thermal ALD using NH ₃ gas, Ni preferentially nucleates at the step edge of HOPG, Thereby forming a wire. In addition, the Ni nanowires grow at two different lateral growth rates depending on the number of ALD cycles, while the vertical growth rate is constant and is similar to the growth rate of Ni film on SiO ₂ . These two steps are explained by the coalescence and grain coarsening of Ni nuclei formed along the step edge in the initial growth region and the selective nucleation of existing nanowires.

In addition, it has been found that NH ₃ gas exposure of HOPG does not significantly change surface properties based on XPS results. On the other hand, Ni can be deposited on the entire HOPG by introducing a PE-ALD process or pretreating HOPG with NH ₃ plasma. In addition, the generation of nitrogen species on the entire HOPG surface was confirmed by XPS analysis. The DFT results have shown that by stabilizing the adsorbed state of the surface nitrogen species of the plasma treated HOPG, it is possible to improve the chemisorption of the Ni precursor. These results provide insight into the initial growth mechanism of metal ALD on the carbon surface and show that ALD Ni can be extended for various applications.

Claims (11)

A method of manufacturing a nano material comprising depositing nickel on the surface of a carbon material by atomic layer deposition,
(a) an exposure step of adsorbing a nickel precursor on a surface of a carbon material to adsorb it;
(b) purging the unadsorbed nickel precursor;
(c) reacting the nickel precursor adsorbed carbon material with the reactants; And
(d) a final purging step of removing remaining unreacted material after completion of the reaction,
Wherein the reactant is NH ₃ gas or NH ₃ plasma.
The method according to claim 1,
Wherein the NH ₃ gas is injected at a temperature of 50 to 100 ° C at a flow rate of 100 to 400 sccm for 5 to 10 seconds.
The method according to claim 1,
Wherein the NH ₃ plasma is performed by applying a power of 100 to 400 W for 5 to 10 seconds.
The method according to claim 1,
Wherein the step (a) comprises pretreating the carbon material with a reactant prior to the introduction of the nickel precursor.
The method according to claim 1,
Wherein the nickel deposited on the surface of the carbon material is formed of a nanowire or a nanofilm.
6. The method of claim 5,
Wherein the nanowire is formed along a step edge of a surface of a carbon material.
The method according to claim 1,
Wherein the cycle consisting of the steps (a) to (d) is repeatedly performed.
8. The method of claim 7,
Wherein the nanowires deposited on the carbon surface have a longer length or a greater thickness of the nanofilm as the number of cycles increases.
The method according to claim 1,
The carbon material is graphite,
Wherein the nickel precursor is nickel (1-dimethylamino-2-methyl-2-butanolate) ₂ .
A catalyst comprising a nanomaterial produced according to any one of claims 1 to 9.
An electrode comprising a nanomaterial produced according to any one of claims 1 to 9.

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