CN108441841B - A kind of method of growing transition metal dichalcogenide thin film - Google Patents

Abstract

The invention discloses a method for growing a transition metal disulfide film, which adopts a metal amidinate compound as a metal precursor, H₂S plasma is used as a sulfur source to synthesize pyrite FeS by an ALD process₂，CoS₂And NiS₂A film. The FeS of the invention₂，CoS₂And NiS₂The deposition process follows the ideal growth behavior of layer-by-layer ALD in a wide deposition temperature range, and can obtain a transition metal disulfide film with a pyrite structure with very pure components and smooth surface. Further, the ALD process of the present invention deposits FeS₂，CoS₂And NiS₂The thin film can be conformally deposited at aspect ratios as high as 10: 1, thereby representing the broad and promising applicability of this ALD process for conformal thin film deposition on complex high aspect ratio 3D architectures.

Description

A kind of method of growing transition metal dichalcogenide thin film

technical field

The invention relates to the technical field of thin film preparation, in particular to a method for growing a transition metal disulfide thin film.

Background technique

Pyrite-type transition metal dichalcogenides ( _denoted as MS2, where M=Fe, Co, Ni) are capable of forming a series of very useful compounds in many ways. Because the pyrite series compounds have the same crystal structure (space group: Pa-3), but the gradual increase of antibonding d electrons in the conduction band is different, therefore, metallic pyrite exhibits very different electrical and magnetic properties nature. For example, iron pyrite (FeS ₂ ) is a diamagnetic semiconductor, cobalt pyrite (CoS ₂ ) is a roving electron ferromagnet, and pyrite (NiS ₂ ) is an antiferromagnetic semiconductor. These different material properties not only provide a model system platform for the scientific research of pyrite basic materials, but also provide a broader material engineering platform for various important applications. Especially the low-cost and abundant pyrite FeS ₂ , CoS ₂ and NiS ₂ have recently shown extremely high application prospects in many cutting-edge energy technologies, such as, solar cells, lithium, sodium-ion batteries, electrocatalytic hydrogen production , electrocatalytic oxygen production and electrocatalytic oxygen reduction. However, for many practical engineering applications and basic scientific research, metallic pyrite materials need to be synthesized as thin films. Typical methods for synthesizing pyrite thin films MS2 ₍ M=Fe, Co, Ni) include sputtering and chemical vapor deposition targeting sulfides or sulfidation by sulfiding related metal or oxide films. But these methods often have limitations in film quality (eg, impurities and roughness) and process controllability. In addition to the above-mentioned processes, atomic layer deposition (ALD) technology has recently become a new process technology for synthesizing high-quality thin-film materials. ALD employs a saturated, self-limiting surface chemistry, whereby thin film materials are grown in a layer-by-layer fashion, resulting in highly uniform films on large-area scales and atomically precisely controllable growth of film composition and thickness. At the same time, ALD exhibits excellent conformal thin film deposition properties on almost any complex or porous three-dimensional structure. With these unique advantages, ALD has enabled many important nanomaterial design and engineering over the past few decades.

However, so far, ALD has not reported the process of synthesizing pyrite MS ₂ (M=Fe, Co, Ni). Previous attempts have been made to synthesize sulfides of these metals by ALD using several types of metal-organic precursors and H ₂ S gas as precursor sources, but have all demonstrated close to 1:1 metal-sulfur stoichiometry sulfide, that is, a metal-sulfide.

Therefore, the existing technology still needs to be improved and developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a method for growing a transition metal disulfide thin film, aiming to solve the problem that the sulfidation of the metal-sulfur stoichiometric ratio close to 1:1 prepared by the existing ALD method matter problem.

The technical scheme of the present invention is as follows:

The present invention provides a method for growing a transition metal disulfide thin film. As shown in the following formula (1), a transition metal amidine compound is used as a metal precursor, and H ₂ S plasma is used as a sulfur source, and the transition metal disulfide is formed by an ALD method. Sulfide MS ₂ thin films, where M=Fe, Co or Ni;

The transition metal amidine-based compound is an iron amidine-based compound, a cobalt amidine-based compound or a nickel amidine-based compound.

The invention adopts the metal amidine compound as the metal precursor and the H ₂ S plasma as the sulfur source, and synthesizes the pyrite FeS ₂ , CoS ₂ and NiS ₂ thin films through the ALD process. The deposition process of FeS ₂ , CoS ₂ and NiS ₂ in the present invention follows the ideal growth behavior of layer-by-layer ALD in a wide range of deposition temperature, and can obtain transition metals of pyrite structure with very pure composition and smooth surface Disulfide films. Further, the FeS ₂ , CoS ₂ and NiS ₂ thin films deposited by the ALD process of the present invention can be conformally deposited in trenches with an aspect ratio of up to 10:1, which shows that the ALD process can be used in complex and high aspect ratio applications. Broad and promising applicability for conformal thin film deposition on 3D architectures.

Preferably, the iron amidine compound is selected from bis(N,N'-diisopropyl(methyl-butyl)amidino)iron, bis(N,N'-bis(methyl,ethyl)yl(methyl-butyl) ) amidinyl) iron, bis(N,N'-bis(tert, iso, n-)butyl(form-butyl)amidino)iron, bis(N,N'-bis(tert, iso, normal, ring) One of pentyl (form-butyl) amidino) iron and bis(N,N'-dicyclohexyl (form-butyl) amidino) iron. More preferably, the iron amidine compound is bis(N,N'-di-tert-butylacetamidino)iron(II) (Fe(amd) ₂ ).

Preferably, the cobaltamidinyl compound is selected from bis(N,N'-diisopropyl(methyl-butyl)amidino)cobalt, bis(N,N'-bis(methyl,ethyl)yl(methyl-butyl) ) amidinyl) cobalt, bis(N,N'-bis(tertiary, iso, n-)butyl (form-butyl)amidino) cobalt, bis(N,N'-bis(tertiary, iso, normal, ring) One of pentyl (form-butyl) amidino) cobalt and bis(N,N'-dicyclohexyl (form-butyl) amidine) cobalt. More preferably, the cobalt amidine compound is bis(N,N'-di-tert-butylacetamidino)cobalt(II) (Co(amd) ₂ ).

Preferably, the nickel amidine compound is selected from bis(N,N'-diisopropyl(methyl-butyl)amidino)nickel, bis(N,N'-bis(methyl,ethyl)yl(methyl-butyl) ) amidinyl) nickel, bis(N,N'-bis(tertiary, iso, n-)butyl(form-butyl)amidino)nickel, bis(N,N'-bis(tertiary, iso, normal, ring) One of pentyl (form-butyl) amidine) nickel and bis(N,N'-dicyclohexyl (form-butyl) amidine) nickel. More preferably, the nickel amidine compound is bis(N,N'-di-tert-butylacetamidino)nickel(II) (Ni(amd) ₂ ).

The method for growing a transition metal dichalcogenide film of the present invention, wherein, specifically includes:

Step S10, delivering the transition metal amidine compound vapor into the reaction chamber of the ALD reactor, where the transition metal amidine compound vapor acts as a metal precursor and is chemically adsorbed on the substrate surface of the reaction chamber;

Step S20, then transporting the H ₂ S plasma into the reaction chamber, where the H ₂ S plasma acts as a sulfur source to react with the metal precursor chemically adsorbed on the surface of the substrate to form a thin film;

Steps S10 and S20 are repeated to form an MS ₂ thin film on the surface of the substrate.

The characteristic of the ALD process is that in each growth cycle, only a single atomic layer film is deposited, and its growth is self-limited. During the film growth process of the ALD process, after the chemical adsorption on the substrate surface is saturated, the number of surface reaction precursors no longer increases with time, so the film grown in each cycle is only a single atomic layer. Compared to other deposition methods, the ALD process produces very pure films and allows precise control of film thickness and composition. The simultaneously grown films have good conformality to the substrate.

Preferably, in the step S10, by heating the transition metal amidine compound to 40-200° C., the vapor of the transition metal amidine compound is transported into the reaction chamber of the ALD reactor with the aid of an inert gas.

Preferably, in the step S20, the H ₂ S plasma is generated by the excitation of the H ₂ S gas or the H ₂ S gas diluted by the inert gas coupled into the radio frequency.

Preferably, after the step S10, and before the step S20, the step includes: introducing an inert gas into the reaction chamber of the ALD reactor, and purging the excess metal precursor and its by-products out of the reaction chamber.

Preferably, after the step S20, before repeating the steps S10 and S20, the steps include: introducing an inert gas into the reaction chamber of the ALD reactor, and purging the excess metal precursor, sulfur source and its by-products out of the reaction room.

In the step S20, the reaction temperature is 80-300°C.

In the present invention, the substrate is a Si wafer or a SiO ₂ substrate, or a carbon-based powder material substrate, etc., or a planar SiO ₂ /Si substrate (ie, a Si wafer with 200 nm thermally grown SiO ₂ ).

Specifically, the method for growing a transition metal dichalcogenide film of the present invention mainly includes the following steps: (1) the metal precursor enters the reaction chamber in the form of gas, and is chemically adsorbed on the surface of the substrate; (2) the excess metal is removed with an inert gas The precursor and its by-products are swept out of the reaction chamber; (3) the sulfur source enters the reaction chamber in the form of plasma and reacts with the metal precursor adsorbed on the substrate surface last time; (4) an inert gas is used again The excess reaction precursor and its by-products are purged out of the reaction chamber; the above steps (1)-(4) are repeated to form the desired MS ₂ thin film.

Beneficial effects: The present invention adopts metal amidine compound as metal precursor and H ₂ S plasma as sulfur source, and synthesizes pyrite FeS ₂ , CoS ₂ and NiS ₂ thin films by ALD process. The deposition process of FeS ₂ , CoS ₂ and NiS ₂ in the present invention follows the ideal growth behavior of layer-by-layer ALD in a wide range of deposition temperature, and can obtain transition metals of pyrite structure with very pure composition and smooth surface Disulfide films. Further, the FeS ₂ , CoS ₂ and NiS ₂ thin films deposited by the ALD process of the present invention can be conformally deposited in trenches with an aspect ratio of up to 10:1, which shows that the ALD process can be used in complex and high aspect ratio applications. Broad and promising applicability for conformal thin film deposition on 3D architectures.

Description of drawings

Figure 1: (a) The relationship between increasing M(amd) ₂ exposure and its corresponding change in film growth rate at a fixed H ₂ S plasma pulse duration of 15 s; (b) at a fixed M(amd) ₂ The relationship between the increase of H ₂ S plasma pulse time length and its corresponding change in film growth rate when the exposure amount is about 0.09 Torrsecond; (c) the change of S/M atomic ratio relative to the increase of H ₂ S plasma pulse time length; (d) The film thickness as a function of the number of ALD cycles; (e) The film growth rate as a function of deposition temperature; (f) The S/M atomic ratio as a function of deposition temperature; (ad) The deposition temperature was 200 °C, (e, f) Using saturated M(amd) ₂ exposure (~0.09 Torr sec) and H2S plasma pulse duration ( ₁₅ s).

Figure 2 shows the TEM images and corresponding electron diffraction patterns of ALD (a, b) deposited FeS ₂ , (c, d) CoS ₂ and (e, f) NiS ₂ thin films.

Figure 3 shows the Raman spectra of ALD-deposited FeS ₂ , CoS ₂ and NiS ₂ films; all films were deposited at 200°C for 200 ALD cycles.

Figure 4. XPS (a) full spectrum and (b) N 1s, (c) C 1s, (d) O1s, (e) Fe 2p, (f) Co of ALD-deposited FeS ₂ , CoS ₂ and NiS ₂ films High-resolution spectra of 2p, (g) Ni 2p, (h) S 2p, films deposited at 200 °C for 200 cycles; note that the spectra shown in Fig. 4(ad) are all at 2keV Ar + sputtering for 10 s After the results, this was done to remove carbon contamination on the sample surface.

(a, d) SEM and (df) AFM images of (a, d) FeS ₂ , (b, e) CoS ₂ and (c, f) NiS ₂ thin films deposited by ALD at 200 °C for 200 cycles in Fig. 5; (gi ) Cross-sectional SEM images of ALD-deposited conformal trench structures with an aspect ratio of 10:1; ALD deposition periods are (g) 300-cycle _FeS2 , (h) ₂₀₀ -cycle CoS2 and (i) 200 cycles, respectively - Cyclic NiS ₂ .

Detailed ways

The present invention provides a method for growing a transition metal dichalcogenide thin film. In order to make the purpose, technical solution and effect of the present invention clearer and clearer, the present invention is further described below in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The method for growing a transition metal dichalcogenide thin film provided by this embodiment includes the following steps:

Using bis(N,N'-di-tert-butylacetamidino)iron(II)(Fe(amd) ₂ ), bis(N,N'-di-tert-butylacetamidino)cobalt(II)(Co( amd) ₂ ) and bis(N,N'-di-tert-butylacetamidino)nickel(II) (Ni(amd) ₂ ) as metal precursors and H ₂ S plasma as co-reactant, in a self-made tubular Atomic layer deposition (ALD) of MS2 ₍ M=Fe, Co, Ni) thin films was performed in an ALD reactor. The metal precursors were kept in different glass containers, and they were heated to 70°C during deposition to provide sufficient vapor pressure. The metal precursor vapor was transported into the reaction chamber with the aid of purified N carrier gas (through a Gatekeeper inert gas purifier ₎ . The H ₂ S plasma was generated by in-coupled radio frequency (RF) excitation at a fixed flow (50 sccm) of dilute H ₂ S (3% by volume of Ar gas mixed with H ₂ S), and in order to generate a stable Plasma, the RF was turned on to obtain plasma 6 s after H ₂ S started to flow in each ALD cycle. _In this work, the RF power was 80 W, and the H2S plasma was excited in the upstream region of the quartz tube in the ALD reactor. Using purified _N2 gas (100 sccm) as the purge gas, it was experimentally found that the _N2 purge for 30 s was sufficient to completely remove by-products and excess precursors. The deposition temperature varied from 80 to 300°C. The growth behavior of ALD films was investigated by varying the amount of metal precursor dose and thus the exposure of the metal precursor in each ALD cycle. Planar SiO ₂ /Si substrates (ie Si wafers with 200 nm thermally grown SiO ₂ ) were used to study the thin film growth behavior and in most cases thin film characterization. All substrates were sequentially cleaned with acetone, methanol and isopropanol, and then pretreated with H2S plasma for ₃ min before deposition.

Characterization of the transition metal dichalcogenide film in this example:

The thickness of ALD _- deposited MS2 (M=Fe, Co, Ni) films was measured by X-ray reflectance (XRR, Bruker, D8 Advance) and by X-ray fluorescence (XRF, Rigaku, ZSX Primus II) and cross-sectional scanning Electron microscopy (SEM, Zeiss, SUPRA55) was used to verify the thickness values of the samples. XRF was used to obtain the S/M (M=Fe, Co, Ni) atomic ratio of the MS ₂ film. The microstructure and crystal structure of the ALD films were obtained by transmission electron microscopy (TEM, Jeol, JEM-3200FS). The crystal structure was analyzed using Raman spectroscopy (Horiba, LabRAM HR800) with an excitation wavelength of 532 nm. Thin films for Raman analysis were deposited on quartz wafers to avoid background signals from Si. The purity of the films was analyzed using X-ray photoelectron spectroscopy (XPS, Thermo Scientific, Escalab 250Xi). The film surface morphology was characterized using SEM and atomic force microscopy (AFM, Bruker, MultiMode 8), and the conformal characteristics of the films deposited on the trench samples were assessed using SEM.

The test results of this embodiment are as follows:

(1), the typical ALD saturation behavior of the growth rate (film thickness increase per ALD cycle) of _FeS2 , CoS2 and _NiS2 films deposited at ₂₀₀ °C is demonstrated in Fig. 1a,b, where the growth rate is Relative to the corresponding metal precursor exposure and the pulse time length of the H ₂ S plasma in each ALD cycle, respectively. As shown in Fig. 1a, when the exposure of the metal precursor M(amd) ₂ (M=Fe, Co, or Ni) increases while the pulse duration of the H ₂ S plasma of 15 s is kept constant, the With M(amd) ₂ exposure exceeding ~0.09 Torrsec, each MS ₂ film first increases and then saturates. Similarly, as shown in Fig. 1b, the growth rate of MS2 (M=Fe, Co or Ni) thin films also increases with _H2 when the exposure of each M(amd) ₂ precursor is fixed at ~0.09 _Torrsec The S plasma pulse time length increases and increases. After more than 5s (for M=Co) or 10s (for M=Fe or Ni), the increase of the plasma pulse length does not cause the increase of the film growth rate, so it reaches saturation. It should be noted that saturation of film growth rate does not necessarily lead to saturation of other film properties such as sulfur content. Therefore, the present example also detected the ratio of sulfur to metal atoms (S/M, where M=Fe, Co or Ni) of the deposited films by X-ray fluorescence spectroscopy (XRF). As shown in Fig. 1c, the S/M ratio also increases with the increase of the H ₂ S plasma pulse duration, and finally saturates at S/M = 2, which means that the present example obtains a stoichiometric MS ₂ ( M=Fe, Co or Ni) thin films. It is further noted that for M=Co or Fe, the minimum plasma pulse length for the saturated S/M ratio is the same as the saturation time for the film growth rate, but for M=Ni a slightly longer H2S plasma of _13s is required volume pulse time to reach S/M saturation. The above results clearly demonstrate that the deposition of MS ₂ (M=Fe, Co, Ni) thin films can follow the ideal ALD behavior with sufficient amounts of metal precursors and co-reactants (sulfur sources) provided, enabling saturation , self-limiting and layer-by-layer thin film growth processes. Therefore, M(amd) ₂ (M=Fe, Co, Ni) exposure and H ₂ S plasma pulse duration used in the following studies were ~0.09 Torrsecond and 15 s, respectively, unless otherwise stated. Under this condition, the thickness of the deposited MS ₂ (M = Fe, Co or Ni) thin films has an ideal linear relationship with the number of ALD cycles (Fig. 1d), indicating that the process can be precisely adjusted by varying the number of deposition cycles Control film thickness. From the slopes of the linear fits shown in Fig. 1d, the growth rates per cycle of the deposited FeS ₂ , CoS ₂ and NiS ₂ films correspond to 0.106, 0.129 and 0.124 nm/cycle, respectively. Additionally, all these linear fits gave negligible ordinate intercept values, suggesting that the nucleation delay process in these ALD processes is negligible.

In addition, the dependence of film growth rate on deposition temperature was investigated. As shown in Fig. 1e, all of these MS ₂ processes show a fairly wide ALD temperature window range of 80°C to at least 200°C, in which the film growth rate only slightly increases with increasing deposition temperature Increase. Above 220 °C, the growth rates of FeS ₂ and CoS ₂ increase significantly with the continued increase of the deposition temperature, which may be caused by the partial decomposition of the metal precursors at high temperature. For NiS ₂ , the temperature window appears to be wider, and the deposition rate remains constant at 280°C with increasing deposition temperature (Fig. 1e). This example further examines the variation of the S/M (M=Fe, Co or Ni) atomic ratio with respect to the deposition temperature. As shown in Fig. 1f, at high deposition temperatures (≥200 °C), all films achieved S/M ratios of 2 (within ±4% error), indicating that stoichiometric MS2 ( _M2 ) was formed at this temperature =Fe, Co, Ni) thin films. But at lower deposition temperatures (80-180°C), although the S/M ratio for M=Ni remains approximately constant, the S/M ratio deviates negatively or positively by 2 for M=Fe or Co, respectively. Therefore, the next material characterization focused on the ALD-deposited MS ₂ films at 200 °C.

(2) The microstructure of the MS ₂ (M=Fe, Co, Ni) thin film deposited by ALD was characterized by TEM. Figure 2 is a TEM image and corresponding electron diffraction pattern of MS ₂ films obtained by ALD deposition at 200°C for 200 cycles (film thickness between 21-26 nm). The analysis found that all these ALD films were well crystallized, and the analysis of electron diffraction patterns further showed that the main crystal structures of FeS ₂ , CoS ₂ and NiS ₂ obtained by ALD deposition were all cubic pyrite structures (space group: Pa-3 ). The extracted lattice constants are a=5.42, 5.54 and 5.67 Angstroms for _FeS2 (PDF#42-1340), CoS2 (PDF# _41-1471 ) and _NiS2 (PDF#11-0099), respectively. The associated Miller indices for the pyrite structure are marked in Fig. 2b,d,f. It is worth noting that while ALD _- deposited CoS and _NiS are pure pyrite phases, ALD pyrite FeS also contains a small amount of marcasite _FeS impurity phase (space group: _Pnnm , PDF#37- 0475), although the diffraction ring in Fig. 2b is somewhat blurred, the corresponding marcasite diffraction ring is observable, and its Miller index is marked with a subscript "M". In fact, it has recently been reported that the presence of marcasite in pyrite _FeS2 is more beneficial for photoelectrochemical applications. In addition, the ALD-deposited MS ₂ thin films at a lower temperature of 120 °C were further investigated, and the obtained TEM images and electron diffraction patterns exhibited roughly the same features as those shown in Fig. 2, indicating that the ALD pyrite MS ₂ (M =Fe, Co, Ni) can be obtained at a fairly wide range of deposition temperatures.

(3), Raman spectroscopic characterization also confirmed the crystal phase results of the MS ₂ thin films deposited by ALD above. As shown in Fig. 3, the Raman spectrum of the ALD-deposited _FeS2 film has three peaks at 319, 336 and 373 cm ^-1 , corresponding to the Ag mode of marcasite _FeS2 and the Eg and Ag of pyrite _FeS2 , respectively model. The Raman spectrum of the CoS2 thin film has _three peaks at 289, 393 and 419 cm _- ¹ , corresponding to the Eg, Ag and Tg modes of pyrite CoS2, respectively. The Raman spectrum of the _NiS2 thin film has three peaks at 282, 477 and 487 cm ^-1 , corresponding to the Eg, Ag and Tg modes of pyrite _NiS2 , respectively. In addition, it is noted that element S (such as _S8 and _S6 ) usually has multiple intense Raman peaks in the region of 400-500 cm ^-1 and below 300 cm ^-1 , but the Raman spectrum does not contain these characteristic peaks, which indicates that ALD The MS ₂ (M=Fe, Co, Ni) films deposited by the process do not contain elemental S impurities.

(4) The purity of ALD-deposited MS ₂ (M=Fe, Co, Ni) thin films was evaluated using X-ray photoelectron spectroscopy (XPS). Representative XPS results for ALD-deposited FeS ₂ , CoS ₂ and NiS ₂ films are presented in Figure 4, the films were deposited at 200 °C for 200 cycles. Figure 4a shows the full-spectrum measurements of the ALD-deposited MS ₂ thin films, where all the peaks can be annotated to the photoelectron emission of the corresponding metal elements (i.e., Fe, Co or Ni) and S. The high-resolution 1s core layer spectra of possible N, C, and O impurities are shown in Fig. 4b–d, and no observable signal appears in the spectra, which indicates that the ALD-deposited MS ₂ film is very pure and the presence of N, C, and O was lower than the detection limit of XPS (0.1 at.%). Similar observations were found for films deposited at lower temperatures: N, C and O impurity signals were also not observed in MS ₂ (M=Fe, Co, Ni) films deposited at 120 or 160 °C. It should be noted that the above-mentioned spectral data for impurity analysis of thin films (Fig. 4a-d) were obtained after removal of carbon contamination on the sample surface after 2keV Ar ⁺ sputtering for 10s, but for the following analysis of transition metals and S elements , using the spectrum of the unsputtered sample, thus avoiding possible data distortion caused by sputtering. As shown in Fig. 4e,f,g, the Fe 2p spectrum of the ALD-deposited _FeS2 film shows a pair of spin-orbit splitting peaks at 707.3 eV (2p _3/2 ) and 720.0 eV (2p _1/2 ), respectively, ALD The Co 2p spectrum of the as-deposited CoS ₂ film shows a pair of spin-orbit splitting peaks at 778.7 eV (2p _3/2 ) and 793.6 eV (2p _1/2 ), and the Ni 2p spectrum of the ALD-deposited NiS ₂ film at 853.7 eV (2p _3/2 ) and 871.2 eV (2p _1/2 ) show a pair of spin-orbit splitting peaks, which are consistent with the values reported in the literature for the corresponding metal dichalcogenides. The S 2p spectra of ALD-deposited FeS ₂ , CoS ₂ and NiS ₂ films are shown in Fig. 4h, where all three spectra show a pair of self-isolation at 162.5 eV (2p _3/2 ) and 163.7 eV (2p _1/2 ) Similar features of the spin-orbit splitting peak, which are consistent with the values for the metal-coordinated S2 ^2- dimer, suggest that metal disulfides are formed. It should be noted that although these samples were exposed to air prior to measuring XPS, no sulfate species were detected at ~168 eV, suggesting that these ALD-deposited MS ₂ films have good resistance to air oxidation. Furthermore, no signal for elemental S at 164.0 eV (2p _3/2 ) and 165.2 eV (2p _1/2 ) was observed in the S 2p spectrum (Fig. 4h), so this also indicates that the ALD-deposited MS ₂ film is also not Contains element S impurities.

(5) Surface morphology of ALD-deposited MS ₂ (M=Fe, Co, Ni) thin films characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As shown in Fig. 5a–e, the top-view SEM and AFM images show that all ALD-deposited MS ₂ films (deposited at 200 °C) are uniform and smooth. The rms roughness values (extracted from AFM) of _FeS2 , CoS2 and _NiS2 films deposited by ALD for ₂₀₀ cycles (film thickness 21-26 nm) are 2.06, 0.78 and 1.38 nm, respectively, and these values are only 3 to 10% of the film thickness. In addition, it was found that smoother-surfaced films could be obtained by lowering the deposition temperature: the ALD films deposited at 120 °C for ₂₀₀ cycles showed rather small rms roughness values, the roughness of _FeS2 , CoS2 and _NiS2 , respectively 0.88, 0.43 and 0.46nm, these values correspond to only 1.7-4% of the film thickness.

Finally, the step coverage of the deposition process was evaluated by depositing a thin film of MS ₂ (M=Fe, Co, Ni) into deep narrow trenches. Using the ALD process described above, 300 cycles of FeS ₂ , 200 cycles of CoS ₂ and 200 cycles of NiS ₂ films were deposited into 2 μm deep trenches with aspect ratios up to 10:1, respectively. As can be seen from the cross-sectional SEM images shown in Fig. 5g–i, benefiting from the self-limiting surface chemistry of ALD, all the deposited MS ₂ films were able to conformally cover the trenches and the film thickness was highly uniform throughout the trenches. . These results clearly demonstrate the excellent step coverage capability of the ALD process, and further demonstrate that these processes can be used for uniform conformal MS ₂ (M=Fe, Co, Ni) thin film deposition of complex 3D structures, and thus have high High prospects and wide applicability.

In summary, in the method for growing transition metal disulfide thin films provided by the present invention, the present invention uses metal amidine compounds (M(amd) ₂ , M=Fe, Co, Ni) as metal precursors, H ₂ S plasma Using the bulk as a sulfur source, transition metal dichalcogenide films were synthesized by ALD process. All the processes of the present invention have been shown to follow the ideal self-limiting ALD growth behavior, resulting in fairly pure, smooth, well-crystallized, stoichiometric pyrite FeS ₂ , CoS ₂ and NiS ₂ thin films. These results suggest that H2S plasma is an efficient sulfur source for ALD of high sulfur _- containing compounds. It is further demonstrated that _FeS2 , CoS2 and _NiS2 thin films can be conformally deposited into narrow trenches with aspect ratios up to 10: ₁ using the ALD process, indicating that these processes can be used on complex or porous 3D nanostructures Uniform conformal thin film deposition. Therefore, these ALD processes will have broad applications in nanoscience and nanoengineering.

It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (8)

1. A method for growing a transition metal disulfide film is characterized in that a transition metal amidinate compound is used as a metal precursor, H₂S plasma as a sulfur source for formation of transition metal disulfides MS by ALD method₂A thin film, wherein M ═ Fe, Co, or Ni;

the transition metal amidino compound is an iron amidino compound, a cobalt amidino compound or a nickel amidino compound;

the formation of transition metal disulfides MS by ALD method₂Conditions of the film: the deposition temperature is 80-300 ℃;

the method for growing the transition metal disulfide film specifically comprises the following steps:

step A, delivering transition metal amidinate vapor into a reaction chamber of an ALD reactor, wherein the transition metal amidinate vapor serves as a metal precursor and is chemically adsorbed on the surface of a substrate in the reaction chamber;

step B, followed by reaction of H₂S plasma is delivered into the reaction chamber, the H₂The S plasma is used as a sulfur source to react with a metal precursor chemically adsorbed on the surface of the substrate to form a film;

repeating step A, B to form MS on the surface of the substrate₂A film;

the transition metal disulfide thin film is uniformly conformally deposited onto the three-dimensional structure.

2. The method of growing a transition metal disulfide thin film of claim 1, wherein the ferric amidinate compound is selected from one of bis (N, N ' -diisopropyl (methyl-butyl) amidinate) iron, bis (N, N ' -di (methyl, ethyl) (methyl-butyl) amidinate) iron, bis (N, N ' -di (tert, iso, N) butyl (methyl-butyl) amidinate) iron, bis (N, N ' -di (tert, iso, N, cyclo) pentyl (methyl-butyl) amidinate) iron, bis (N, N ' -dicyclohexyl (methyl-butyl) amidinate) iron.

3. The method of growing a transition metal disulfide thin film according to claim 1, wherein the cobalt amidinate compound is selected from one of bis (N, N ' -diisopropyl (methyl-butyl) amidinate) cobalt, bis (N, N ' -di (methyl, ethyl) (methyl-butyl) amidinate) cobalt, bis (N, N ' -di (tert-, iso-, N) -butyl (methyl-butyl) amidinate) cobalt, bis (N, N ' -di (tert-, iso-, N-, cyclo) pentyl (methyl-butyl) amidinate) cobalt, bis (N, N ' -dicyclohexyl (methyl-butyl) amidinate) cobalt.

4. The method of growing a transition metal disulfide thin film of claim 1, wherein the nickel amidinate compound is selected from one of bis (N, N ' -diisopropyl (methyl-butyl) amidinate) nickel, bis (N, N ' -di (methyl, ethyl) (methyl-butyl) amidinate) nickel, bis (N, N ' -di (tert, iso, N) butyl (methyl-butyl) amidinate) nickel, bis (N, N ' -di (tert, iso, N, cyclo) pentyl (methyl-butyl) amidinate) nickel, bis (N, N ' -dicyclohexyl (methyl-butyl) amidinate) nickel.

5. The method of growing a transition metal disulfide thin film according to claim 1, wherein in step a, the transition metal amidinate compound vapor is delivered to the reaction chamber of the ALD reactor with the aid of an inert gas by heating the transition metal amidinate compound to a temperature of 40-200 ℃.

6. The growing transition metal disulfide of claim 1A method of forming a thin film, wherein in the step B, the H is₂S plasma is by H₂S gas or H diluted with inert gas₂S gas is generated by the coupled-in rf excitation.

7. The method of growing a transition metal disulfide thin film of claim 1, wherein after said step a, said step B comprises, before: and introducing inert gas into the reaction chamber of the ALD reactor, and purging the redundant metal precursor and the by-product thereof out of the reaction chamber.

8. The method for growing a transition metal disulfide thin film according to claim 1, wherein in step B, the temperature of the reaction is 80-300 ℃.

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