Microneedle growth method as an innovative approach for growing freestanding single crystal diamond substrate: Detailed study on the growth scheme of continuous diamond layers on diamond microneedles

Accepted Manuscript Microneedle growth method as an innovative approach for growing freestanding single crystal diamond substrate: Detailed study on the growth scheme of continuous diamond layers on diamond microneedles

Hideo Aida, Seong-Woo Kim, Kenjiro Ikejiri, Daiki Fujii, Yuki Kawamata, Koji Koyama, Hideyuki Kodama, Atsuhito Sawabe PII: DOI: Reference:

S0925-9635(16)30603-3 doi: 10.1016/j.diamond.2016.12.016 DIAMAT 6783

To appear in:

Diamond & Related Materials

Received date: Revised date: Accepted date:

4 November 2016 11 December 2016 11 December 2016

Please cite this article as: Hideo Aida, Seong-Woo Kim, Kenjiro Ikejiri, Daiki Fujii, Yuki Kawamata, Koji Koyama, Hideyuki Kodama, Atsuhito Sawabe , Microneedle growth method as an innovative approach for growing freestanding single crystal diamond substrate: Detailed study on the growth scheme of continuous diamond layers on diamond microneedles. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Diamat(2016), doi: 10.1016/j.diamond.2016.12.016

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Microneedle growth method as an innovative approach for growing freestanding single crystal diamond substrate: Detailed study on the growth scheme of continuous diamond layers on diamond microneedles

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Hideo Aidaa*, Seong-Woo Kima, Kenjiro Ikejiria, Daiki Fujiia, Yuki Kawamataa, Koji

Namiki Precision Jewel Co. Ltd., 3-8-22 Shinden, Adachi, Tokyo 123-8511, Japan

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Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258,

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Koyamaa, Hideyuki Kodamab, and Atsuhito Sawabeb

Japan

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*Corresponding author. E-mail: [email protected]

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Highlights 1. Detailed study of the microneedle growth method for diamond substrate fabrication. 2. Stress state changes from compressive to nearly stress-free during growth.

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Abstract A detailed study of diamond growth on diamond microneedles was conducted using micro-Raman spectroscopy of the microneedle and coalescence regions to approach the production of freestanding diamond substrate by heteroepitaxy with the microneedle

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growth method. The high-density non-diamond-phase carbon is contaminated in the

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initial stage of overgrowth of diamond on diamond microneedles, but this completely

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disappears through the quick recovery of the crystallinity of the overgrown diamond layers during the coalescence with the lateral direction growth. We also point out the

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possibility that a strong driving force is applied to the dislocations generated at the regrowth point and at the coalescence front to enhance the mutual annihilation of

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dislocations. In addition, we reveal that the stress state changes from compressive stress in the initial diamond layers to a nearly stress-free state in the bulk layers on the

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microneedles through a momentary tensile stress state at the regrowth point at the tip of

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the microneedle. Overall results indicate the strong feasibility of producing freestanding,

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stress-free, single-crystal diamond substrate by heteroepitaxy.

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1. Introduction High-quality, large-size, single-crystalline diamond (SCD) substrates are highly desired to realize the ultimate diamond semiconductors that enable high-power, high-frequency future applications [1]. In the last decade, SCD substrate production has

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relied on synthesis under high-pressure, high-temperature (HPHT) atmosphere or

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chemical vapor deposition (CVD) substrates on HPHT-diamond seed substrate [2–6].

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However, HPHT-diamond has a limitation in scaling the crystal size because of the severely strict synthesis conditions. CVD substrates also have a limited substrate size

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since the process starts from the HPHT diamond as the seed substrate. To increase the size of the CVD substrates, a complicated approach such as the combination of the

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lift-off process [5,6] and side-surface growth [7] has been reported [8]. Despite the significant effort devoted to the development of diamond devices, the industrialization

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of diamond devices has been disappointing owing to the unclear roadmap for substrate

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scaling up.

To overcome the substrate-size-related issues, the so-called mosaic wafers or tiled

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clones approach was invented as a unique alternative to enlarging the size of the substrate [9,10]. This innovation allowed us to handle diamond substrates using

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industrial-scale equipment for better reliable device processing rather than in-house, laboratory-scale equipment. However, growth defects exist at the coalescence fronts of each seed piece in the mosaic wafers, resulting in unusable areas, and this remains an unavoidable issue of this approach. As a result, the requirement for the substrate, which is upgraded step by step, is such that an apparent size and uniform crystal quality over the whole substrate area is desired. As a further alternative, we have recently reported an innovation in heteroepitaxial

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diamond substrate [11]. Heteroepitaxy has the theoretical possibility of producing SCD the same size as the basal substrates [12–16], and the most promising structure for producing SCD by heteroepitaxy is believed to be diamond/Ir/MgO [17,18]. However, the large mismatch in the coefficient of thermal expansion (CTE) of diamond and the

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MgO substrate actively prevents the growth of diamond layers thick enough for

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producing freestanding SCD substrate, as serious cracks are generated in the structure

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due to the bowing of the structure after the growth of diamond during the temperature reduction from growth to room temperature [15]. Our recent achievement, the

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microneedle growth method, on the other hand, actively exploits the bowing of the structure and prevents cracking in the grown diamond layers [11]. The diamond

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microneedles are fabricated by processing the topmost surface of the heteroepitaxial diamond thin layers, which is followed by the growth of the main body of thick

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diamond layers above the diamond microneedles, resulting in the production of a

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diamond pillar structure surrounded by air. This structure has been proven to flexibly relax the substrate bowing and to prevent serious cracking, resulting in the realization of

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freestanding SCD by heteroepitaxy.

In this paper, we present further details of the effect of the microneedle growth

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method focusing especially on the crystal formation at the initial stage of the overgrown diamond layers. It was reported that the patterning of the diamond nucleation regions or diamond layers enhances the lateral direction overgrowth, which can promote a reduction in the dislocation density by mutual annihilation [11,19–21]. As we have reported in our previous paper, the flat surface of the overgrown diamond layers from the microneedles is obtained by lateral direction coalescence, meaning that the microneedle growth method should bring about an improvement in the crystal quality

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during the coalescence [22]. This should also include a change in the stress state of the grown diamond layers. Therefore, micro-Raman spectroscopy of the microneedle and coalescence regions was conducted to carefully reveal the behavior of crystal formation in the coalescence regions. The effect of the pitch of the microneedles on the dislocation

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density reduction is also discussed by applying the overgrowth of diamond on

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microneedles with different pitches. In addition, we demonstrate the macroscopic

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surface changes during the microneedle growth method, which is of fundamental future necessity for in situ precise control of the growth conditions in the coalescence stage of

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diamond layers.

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2. Experimental procedure

We prepared MgO(001) substrates with dimensions of 10 × 10 × 0.5 mm3. Epitaxial

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Ir was deposited on the MgO substrate by sputtering at 850 °C for 70 min, resulting in a

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thickness of 650 nm. Then, bias-enhanced-nucleation (BEN) treatment was carried out to nucleate diamond on Ir at a temperature of 850 °C for 2 min. After the initial

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preparation of the substrate, diamond layers of 100 μm in thickness were grown by direct current plasma CVD (DCPCVD). The in-house DCPCVD apparatus and the basic

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growth conditions are detailed elsewhere [17,18,23]. The typical full width at half maximum (FWHM) of the X-ray rocking curve for the diamond (004) reflections of the 100-μm-thick layers was 0.20°. Diamond microneedles of approximately 2 and 80 μm in diameter and height, respectively, and different pitches were then fabricated by processing the top most surface using the thermochemical reaction of diamond with Ni in a high-temperature hydrogen environment [11,22,24]. In this study, three samples with different needle

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pitches of 10, 15, and 20 μm, respectively, as shown in Fig. 1, were prepared. By using DCPCVD, an additional 50 μm of diamond layers were overgrown to produce a completely flat surface. The conditions of the diamond growth as well as the diamond microneedle fabrication are detailed in our previous papers [11,22]. After the growth of

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the overgrown diamond layers, the sample was cut and the cross sections were

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examined using micro-Raman spectroscopy. X-ray rocking curve measurements for the

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diamond (004) reflections were also conducted to investigate the effect of the diamond

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microneedle pitch on the dislocation reduction during the coalescence.

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Fig. 1 Detailed schematic of the diamond microneedle geometry.

3. Results and discussion The first question regarding the growth of diamond from diamond microneedles was how a flat and continuous film can be created through coalescence. We discussed the microscopic process schematics in our previous paper [22], and so in the present study,

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we began by expanding on our previous study of the coalescence scheme of the current microneedle growth method to include the macroscopic point of view. The results are shown in Fig. 2 together with a brief summary of the previous report. As the surface of the specimen changes during the coalescence stage, the surface brightness of the

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specimen in the plasma chamber also changes, as shown in Fig. 2. The brightness when

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the diamond surface is macroscopically flat is seen in Fig. 2(a).

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After the growth of the initial diamond layers, the specimen was taken out of the growth chamber and fabrication of the diamond microneedles by processing the initial

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diamond layers in a high-temperature hydrogen chamber was performed before returning the specimen to the plasma chamber for diamond overgrowth on the

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microneedles. A photograph of the entire specimen surface just after the overgrowth started (the plasma was generated) is shown in Fig. 2(b). The surface of the specimen

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with the diamond microneedles is seen to be only slightly shiny because of diffuse

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reflections.

The following overgrowth scheme then occurs [22]. First, only the tip areas of the

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microneedles are gradually enlarged, and a pyramid shape is created on the top of the needles. Coalescence then starts from the bottom of these pyramidal crystals. As faster

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growth from the V shape of the valley between the pyramidal top of the needles occurs once coalescence starts, the V shape gradually becomes flat, resulting in the creation of an inverted pyramid shape between the needles as the intermediate stage of coalescence, which is illustrated in Fig. 2(c). As we use MgO(001) as the basal substrate, the crystal face of the initial diamond layers used for the microneedle production is (001). Therefore, the flat areas between the microneedles obtained at the intermediate stage of coalescence correspond to the (001) face. Through this microscopic change in the

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surface, the surface of the entire specimen exhibits a shiner surface than that with the bare diamond microneedles. The surface tends to show a facetted morphology as the growth proceeds toward the intermediate coalescence stage with the inverted pyramid shape between the needles as in Fig. 2(c). This is the reason for the higher brightness of

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the surface for the intermediate stage of coalescence (Fig. 2(c)) than for the bare

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diamond microneedles (Fig. 2(b)).

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Lateral growth in the [100] and [010] directions then occurs as the (001)-faced flat areas between the microneedles widen, and finally the coalescence enters the final stage,

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namely, the creation of a flat and continuous film as illustrated in Fig. 2(d). When the surface finally becomes a continuous, flat film, the brightness of the surface reduces as

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shown in Fig. 2(d). These results demonstrate that observation of the surface brightness provides an easy and useful indication of the coalesce stage and thus allows us to

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control the growth conditions in real time if needed. This is extremely important

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because it is essential to precisely control the growth conditions to ensure high-quality coalescence for the microneedle growth method as the coalescence region has a strong

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influence on dislocation generation, annihilation, and/or propagation into the growing

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bulk diamond layers.

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Fig. 2 Macroscopic and microscopic observation of the diamond surface and the

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schematics of the process flow.

In addition to the coalescence scheme discussed above, to further understand the diamond crystal formation behavior, cross-sectional micro-Raman spectroscopy of the

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microneedle and coalescence regions was conducted. The positions where the Raman spectra were collected are identified in the micrograph in Fig. 3. It can be seen in the

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figure that the microneedles are surrounded by air and that the diamond growth occurred only from the top of the microneedles. For a better understanding of the position of the microneedles, two microneedles are highlighted by dashed lines. The seven positions marked in Fig. 3 are in the (a) initial diamond layers, (b) middle of the microneedle, (c) start point of the overgrowth, (d) 10 μm above (c), (e) 10 μm above (d), (f) coalescence front, and (g) 10 μm above (f). The positions (d) and (f) are thought to correspond to the stage of early coalescence, namely, the state between those shown in

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Fig. 2(b) and 2(c). The positions (e) and (g) are thought to correspond to the stage of

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intermediate coalescence, namely, the state shown in Fig. 2(c).

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Fig. 3 Raman spectra of cross section of the coalescence regions in the microneedle area. The micrograph shows a cross section of the specimen observed through the microscope

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of the Raman system for focusing the laser. The seven measurement points, a to g, are

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marked in the micrograph, and the corresponding Raman spectra are (a)-(g).

While the initial diamond layer only exhibits a sharp peak corresponding to diamond at 1333.1 cm−1, as shown in Fig. 3(a), the surface of the diamond microneedles includes amorphous-phase carbon contaminations as shown in Fig. 3(b). This would indicate that sp3 carbon changed to another carbon state during the thermochemical

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reaction of diamond with Ni to diffuse into Ni [24] and that most likely some of the carbon atoms remained on the surface of the microneedles. When the microneedles are subjected to the overgrowth, the tips of the diamond microneedles underwent further degradation in crystal quality, as shown in Fig. 3(c), which is represented by the

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weakened intensity of the peak corresponding to diamond against the broad peak

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corresponding to non-diamond carbon. We also see a slight widening of the FWHM of

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the Raman peak for diamond from 3.5 to 5.5 cm−1. However, the crystal quality above the diamond microneedles gradually recovered as the growth proceeded to the

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intermediate stage of coalescence, as shown in Fig. 3(e), through the state of Fig. 3(d). On the other hand, at the coalescence front, we observed a significant degradation in the

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diamond quality as show in Fig. 3(f). The FWHM of the peak related to diamond was 16.5 cm−1, which is the worst value among the seven positions. This suggests that

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dislocations are generated at the coalescence front. Surprisingly, when the growth

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proceeded to the intermediate stage, the crystal quality of the diamond beyond the coalescence front recovered quickly as shown in Fig. 3(g).

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An upward shift of approximately 1 cm−1 from 1332.2 cm−1, typical of diamond [25], was found for the initial diamond layers as well as the middle area of the diamond

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microneedles. This peak shift corresponds to compressive stress [26]. On the other hand, a peak at 1331.5 cm−1, which is downward shifted from 1332.2 cm−1, was seen for the overgrowth start point, as shown in Fig. 3(c), which corresponds to slight tensile stress [26]. After the coalescence started, the tensile stress is relaxed, and the Raman signal stays at approximately 1332.2 ± 0.3 cm−1 in the microneedle as well as the coalescence front and regions beyond (Figs. 3(d)-(g)). The Raman spectra of regions further from the intermediate coalescence stage

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(corresponding to Figs. 2(c), 3(e), and 3(g)) are shown in Fig. 4. The measurement points were approximately 20 and 50 μm beyond the intermediate stage (spectra shown in Fig. 4(a) and (b), respectively), but unfortunately in the present case it was difficult to clarify whether the measurement point was exactly on the microneedle or coalescence

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front. The complete coalescence illustrated in Fig. 2(d) was accomplished in an

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additional 20 μm growth from the intermediate coalescence of Fig. 2(c). As shown in

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Fig. 4(a), the existence of non-diamond carbon inclusions can still be seen in the region of the additional 20 μm growth. However, this is almost gone for the region of

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additional 50 μm growth. The FWHM of the peaks corresponding to the diamond is around 5 cm−1, which suggests the quick recovery of the diamond crystal quality

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occurred presumably by the defect reduction during the final coalescence process with strong lateral overgrowth. A further interesting finding is that the peak position stayed at

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approximately 1332.2 ± 0.1 cm−1 for the Raman spectra in Fig. 4. As we already

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reported in our previous paper, this remained stable even as we grew 1-mm-thick heteroepitaxial diamond layers on the microneedles; the previously reported values of

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the peak position and FWHM were 1332.0 and 3.7 cm−1, respectively [22]. The overall peak shift in the Raman spectrum from the initial diamond to the thick layers via

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microneedles, which corresponds to a change in the stress state from compressive to neutral via tensile, strongly suggests the feasibility of microneedles for strain relief to grow stress-free bulk diamond layers. Table 1 summarizes the FWHM of the X-ray rocking curve for the diamond (004) reflections of the 50-μm-thick overgrown diamond layers as a function of the diamond microneedle pitch. In contrast to the quality of the initial diamond layers, the overgrown layers show better crystal quality. The table shows that a larger pitch tended to lead to

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better quality. We note that there is no noticeable reduction in the FWHM when we directly grew an additional 50-μm-thick layer without microneedles on the initial diamond layers. This can be explained by the strong lateral direction growth that

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occurred after the intermediate stage of coalescence, as shown in Fig. 2.

Fig. 4 Raman spectra of the diamond specimen after coalescence. (a) and (b) are 20 and

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50 μm beyond the intermediate stage, respectively.

Table 1. FWHM of the X-ray rocking curve for diamond (004)

Initial diamond layer

reflections of diamond layers Microneedle pitch (μm)

FWHM (°)

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Overgrown diamond layer

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0.17

It is normal that the direction of the dislocation propagates in the same direction as

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the growth. However, the strong lateral direction growth generates a bending force that

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acts on the dislocations, presumably resulting in the active mutual annihilation of

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dislocations during the later stage of the coalescence. The larger pitch of the diamond microneedles leads to better quality of diamond. In this case, a longer coalesce time is

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required, and as a result, longer and/or stronger lateral growth completes the coalescence. This leads to enhanced mutual annihilation of dislocations. Therefore, the

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specimen with the largest pitch, 20 μm, in the present study exhibited the narrowest FWHM value. The results of the Raman spectroscopy in the present study do not have a

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direct link with dislocations but do indirectly give us indications of the crystal quality,

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as we discussed. Further study is necessary to elucidate the complete mechanism of the microneedle growth method on the crystal quality improvement; however, the outcomes

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of the present study strongly support the hypothesis that the overgrowth of diamond from the microneedles enhances the lateral overgrowth and possibly provides certain

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effects in regards to dislocation density reduction especially at the coalescence region as we observed the quick recovery of the diamond-related peaks in the Raman spectra. This, at the same time, indicates that there is plenty of room to improve the crystal quality of heteroepitaxial diamond by optimizing the geometry of the diamond microneedles and to precisely control the growth conditions of the coalescence. Thus, the in situ reorganization of the coalescence stage, the fundamental importance of which was discussed in the present study, will be an important future task.

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4. Conclusion A detailed study of diamond growth on diamond microneedles was conducted by micro-Raman spectroscopy of the microneedle and coalescence regions. The quality of

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the diamond microneedles was degraded compared to that of the initial diamond layers

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because of the inclusion of non-diamond-phase carbon, which is attributed to the

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fabrication process of the diamond microneedles through the thermochemical reaction with Ni in a high-temperature hydrogen environment. Further degradation occurred

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when the overgrowth of the diamond started. However, the surprisingly quick recovery of diamond crystal quality was confirmed within relatively thin overgrowth layers at the

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coalescence and related lateral overgrowth regions. The initial diamond layers showed compressive stress, but the overgrowth layers exhibited a nearly stress-free state, despite

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the film thickness, through the momentary tensile stress at the regrowth point.

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Consequently, the overall results suggest the strong feasibility of the microneedle

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growth method for the fabrication of high-quality freestanding SCD substrate.

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References 1. R.S. Sussmann (Ed.), CVD Diamond for Electronics and Sensors, Wiley, Chichester, UK, 2009. 2. F.P. Bundy, W.A. Bassett, M.S. Weathers, R.J. Hemley, H.U. Mao, A.F. Goncharov,

PT

The pressure-temperature phase and transformation diagram for carbon; updated

RI

through 1994, Carbon 34 (1996) 141–153.

SC

3. H. Sumiya, N. Toda, Y. Nishibayashi, S. Satoh, Crystalline perfection of high purity synthetic diamond crystal, J. Cryst. Growth 178 (1997) 485–494.

NU

4. H. Sumiya, K. Tamasaku, Large defect-free synthetic type IIa diamond crystals synthesized via high pressure and high temperature, Jpn. J. Appl. Phys. 51 (2012)

MA

090102.

5. Y. Tzeng, J. Wei, J. T. Woo, and W. Lanford, Free-standing single-crystalline

D

chemically vapor deposited diamond films, Appl. Phys. Lett 63 (1993) 2216–2218.

PT E

6. Y. Mokuno, A. Chayahara, and H. Yamada, Synthesis of large single crystal diamond plates by high rate homoepitaxial growth using microwave plasma CVD

CE

and lift-off process, Diamond Relat. Mater. 17 (2008) 415–418. 7. Y. Mokuno, A. Chayahara, Y. Soda, Y. Horino, and N. Fujimori, Synthesizing

AC

single-crystal diamond by repetition of high rate homoepitaxial growth by microwave plasma CVD, Diamond Relat. Mater. 14 (2005) 1743–1746. 8. Y. Mokuno, A. Chayahara, H. Yamada, N. Tsubouchi, Improving purity and size of single-crystal diamond plates produced by high-rate CVD growth and lift-off process using ion implantation, Diamond Relat. Mater. 18 (2009) 1258–1261. 9. G. Janssen. L.J. Giling, “Mosaic” growth of diamond, Diamond Relat. Mater. 4 (1995) 1025–1031.

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10. H. Yamada, A. Chayahara, H. Umezawa, N. Tsubouchi, Y. Mokuno, S. Shikata, Fabrication and fundamental characterizations of tiled clones of single-crystal diamond with 1-inch size, Diamond Relat. Mater. 24 (2012) 29–33. 11. H. Aida, S.-W. Kim, K. Ikejiri, Y. Kawamata, K. Koyama, H. Kodama, A. Sawabe,

PT

Fabrication of freestanding heteroepitaxial diamond substrate via micropatterns and

RI

microneedles, Appl. Phys. Express 9 (2016) 035504.

SC

12. M. Schreck, H. Roll, B. Stritzker, Diamond/Ir/SrTiO3: A material combination for improved heteroepitaxial diamond films, Appl. Phys. Lett. 74 (1999) 650–652.

NU

13. M. Schreck, F. Hörmann. H. Roll, J.K.N. Lindner, B. Stritzker, Diamond nucleation on iridium buffer layers and subsequent textured growth: A route for the realization

MA

of single-crystal diamond films, Appl. Phys. Lett. 78 (2001) 192–194. 14. Z. Dai, C. Badnarski-Meinke, R. Loloee, B. Golding, Epitaxial (100) iridium on

PT E

82 (2003) 3847–3849.

D

A-plane sapphire: A system for wafer-scale diamond heteroepitaxy, Appl. Phys. Lett.

15. S. Gsell, T. Bauer, J. Goldfuß, M. Schreck, B. Stritzker, A route to diamond wafers by

CE

epitaxial deposition on silicon via iridium/yttria-stabilized zirconia buffer layers, Appl. Phys. Lett. 84 (2004) 4541–4543.

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16. M. Fischer, S. Gsell, M. Schreck, R. Brescia, B. Strizker, Preparation of 4-inch Ir/YSZ/Si(001) substrates for the large-area deposition of single-crystal diamond, Diamond Relat. Mater. 17 (2008) 1035–1038. 17. K. Ohtsuka, K. Suzuki, A. Sawabe, T. Inuzuka, Epitaxial growth of diamond on iridium, Jpn. J. Appl. Phys. 35 (1996) L1072–L1074. 18. K. Ohtsuka, H. Fukuda, K. Suzuki, A. Sawabe, Fabrication of epitaxial diamond thin film on iridium, Jpn. J. Appl. Phys. 36 (1997) L1214–L1216.

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19. A. Usui, H. Sunakawa, A. Sakai, A. Yamaguchi, Thick GaN epitaxial growth with low dislocation density by hydride vapor phase epitaxy, Jpn. J. Appl. Phys. 36 (1997) L899–L902. 20. S. Washiyama, S. Mita, K. Suzuki, A. Sawabe, Coalescence of epitaxial lateral

PT

overgrowth-diamond on stripe-patterned nucleation on Ir/MgO(001), Appl. Phys.

RI

Express 4 (2011) 095502.

SC

21. Y. Ando, T. Kamano, K. Suzuki, A. Sawabe, Epitaxial lateral overgrowth of diamonds on iridium by patterned nucleation and growth method, Jpn. J. Appl. Phys.

NU

51 (2012) 090101.

22. H. Aida, K. Ikejiri, S.-W. Kim, K. Koyama, Y. Kawamata, H. Kodama, A. Sawabe,

MA

Overgrowth of diamond layers on diamond microneedles: new concept for freestanding diamond substrate by heteroepitaxy, Diamond Relat. Mater. 66 (2016)

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77–82.

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23. Y. Ando, J. Kuwabara, K. Suzuki, A. Sawabe, Patterned growth of heteroepitaxial diamond, Diamond Relat. Mater. 13 (2004) 1975–1979.

CE

24. A.P. Grigoriev, V.V. Kovalsky, Working of diamond with metal, INDIAQUA 39 (1984) 47–54.

AC

25. D.M. Trucchi, E. Cappelli, G. Conte, G. Mattei, C. Gramaccioni, P. Ascarelli, The influence of grain-boundaries on the electronic performance of CVD diamond films, Diam. Relat. Mater. 14 (2005) 575–579. 26. Y. von Kanel, J. Stiegler, J. Michler, E. Blank, Stress distribution in heteroepitaxial chemical vapor deposited diamond films, J. Appl. Phys. 81 (1997) 1726–1736.

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Graphical Abstract