JP2004060037A - Method for producing diamond and diamond product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing diamond by which diamond of α≤1 can be synthesized at a high efficiency by using an oxygen-containing gas such as carbon dioxide, and to provide a diamond product. <P>SOLUTION: Diamond is subjected to vapor phase synthesis under conditions shown in the following numerical inequality provided that the numerical ratio occupied by hydrogen atoms in a reaction gas is defined as 2x(%), the numerical ratio of carbon atoms as y(%), the numerical ratio of oxygen atoms as z(%), and a substrate temperature as T(°C): T>33500×(y-z)/(x+y-z)+717T<254000×(y-z)/(x+y-z)+717T<1100. The reaction gas comprises hydrogen, methane and carbon dioxide. The reaction gas is made into a plasma state by microwaves of ≥5 kW to produce the diamond by the vapor phase synthesis. <P>COPYRIGHT: (C)2004,JPO

Description

【００４１】
次に、α値の算出方法（２とおり）について説明する。先ず、第１の方法は以下のとおりである。
１）基板表面を傷つけ処理（スクラッチ処理）した後、予め１〜数μｍのダイヤモンド結晶粒子を基板上に成長させた。このときの成長条件は、下記３）における成長速度を求めやすくするため、｛１００｝面と｛１１１｝面の両方が明確に現れるようにした。即ち、α＝１．５〜２付近に相当する成長条件を使用した。２）次に、この｛１００｝面と｛１１１｝面の双方が現れたダイヤモンド結晶粒子の大きさを測定した。具体的には、電子顕微鏡観察により各結晶面の縁の長さを測定し、各結晶面の相対角度が結晶学上既知であるので、この結晶粒子の形状と大きさを決定した。なお、測定対象の結晶粒子には、２個以上の結晶粒子が近接していないものを選んだ。もし、成長中に結晶粒子が接触すると、接触面側ではそれ以上成長できないので、正確な成長量を測定できないからである。
３）次に、この結晶粒子を種として、各条件で１〜２時間成長を行った。
４）成長後の結晶の形状と大きさを、２）と同様な方法で決定した。
５）２）と４）で得られた結晶粒子の形状と大きさを比較し、［１００］方向及び［１１１］方向に夫々いくら成長したかを幾何学的に算出した。成長量を成長時間により規格化し、成長速度を求めた。結晶粒子が成長せず、逆に小さくなったときは、プラズマ曝露によってダイヤモンド粒子がエッチングされたことになる。このとき、成長量及び成長速度は負の値となる。なお、［１００］方向及び［１１１］方向は、夫々｛１００｝面の法線方向及び｛１１１｝面の法線方向に相当する。
【００４２】
次に、αパラメータの算出方法についての第２の方法について説明する。
１）基板表面を傷つけ処理（スクラッチ処理）した後、直接、各条件で数μｍまでダイヤモンド成長を行った。このとき、成長前の結晶粒子の大きさは０と見なせる。但し、スクラッチ処理により、基板（実施例ではシリコン）に微小な傷が付き、そこを基点にダイヤモンドの成長が始まる。一方、スクラッチ処理は通常ダイヤモンド粉末で行うため、その欠片が基板上に残り、それが種となって成長する場合もある。しかしながら、欠片はほとんどの場合０．１μｍ以下であるので、成長を数μｍ実施すれば、いずれにしても初期値は、実質的な大きさが０であると見なすことができる。
２）第１の方法の２）と同様にして、結晶粒子の形状と大きさを決定した。
３）幾何学的に、［１００］方向及び［１１１］方向の成長量を算出し、成長時間で規格化して、成長速度を求めた。
【００４３】
なお、αパラメータの値が１を超え３未満の場合、即ち｛１００｝面と｛１１１｝面の双方が現れる場合に限り、第２の方法を使用することができる。しかしながら、第２の方法では、α≦１、α≧３の値を決定できないので、第１の方法を使用すべきである。
【００４４】
但し、表１、試料番号２４〜２８に限っては、第２の方法に従ってダイヤモンドの成長を行い、｛１１１｝面のみで覆われた結晶が得られたため、正確なαパラメータが求められず、α≧３と表記した。
【００４５】
前記表１に示すように、合成条件によっては、ダイヤモンド粒子がエッチングされて、小さくなった。図２（ａ）、（ｂ）は夫々有効炭素濃度０（ＣＯ_２／ＣＨ_４＝１．０）の場合のプラズマ曝露前後における基板表面のダイヤモンド粒子の形状を走査型電子顕微鏡により撮影した写真である。図２（ａ）は成長前のダイヤモンド粒子を示し、図２（ｂ）は追成長後、エッチングされた後のダイヤモンド粒子を示す。この図２（ａ）、（ｂ）に示すように、追成長により、ダイヤモンド粒子がエッチングされて小さくなっている。
【００４６】
なお、「有効炭素濃度」とは、反応ガス中に占める水素原子数比を２ｘ（％）、炭素原子数比をｙ（％）、酸素原子数比をｚ（％）としたとき、下記数式４にて表されるｃのことをいう。
【００４７】
【数４】
ｃ＝（ｙ−ｚ）／（ｘ＋ｙ−ｚ）×１００（％）
【００４８】
この有効炭素濃度は、反応ガス中の酸素原子と炭素原子を相殺し、余剰の炭素原子と水素分子との仮想的な分圧比を示すものであるが、本願発明者等は、この数式４で表される有効炭素濃度ｃがダイヤモンド成長に寄与する炭素濃度を表すと仮定して、合成条件と合成結果とを分類することにより、その相関性を表すことができることを知見した。
【００４９】
図３は、横軸に有効炭素濃度ｃ（％）をとり、縦軸に基板温度Ｔ（℃）をとって、両者の関係を示すグラフ図である。図中、×はダイヤモンドが成長せず、ダイヤモンドがエッチングされた実験条件である。また、■はα≦１、●は１＜α＜３、▲はα≧３となった実験条件を示す。この図３に示すように、結果として、線分Ｌ１（実直線）の近傍がエッチングと成長との境界線、線分Ｌ２（破線）の近傍がα＝１、線分Ｌ３（実曲線）近傍がα＝３となる。これらの線分を数式で表すと、下記数式５乃至７となる。
【００５０】
【数５】
線分Ｌ１：Ｔ＝２５４０ｃ＋７１７　　　　　　：エッチングと成長の境界線
【００５１】
【数６】
線分Ｌ２：Ｔ＝３３５ｃ＋７１７　　　　　　　：α＝１
【００５２】
【数７】
線分Ｌ３：Ｔ＝８９Ｌｎ（ｃ）＋８６９　　　　：α＝３（Ｌｎは自然対数）
【００５３】
α≒１の例として、試料番号５及び１１の走査型電子顕微鏡写真を夫々図４（ａ）及び（ｂ）に示す。図４（ａ）は、ほぼ正確にα＝１であり、双晶の集合体も見られるものの、全てが正方形の｛１００｝面のみからなる結晶が成長している。そのいくつかに見られるように、双晶のないものは立方体となっていることがわかる。図４（ｂ）は、立方体の頂点に極めて小さな正三角形の｛１１１｝面が見られ、α値はごく僅かに１からずれている。
【００５４】
α＜１の例として、試料番号６及び９の走査電子顕微鏡写真を夫々図５（ａ）及び（ｂ）に示す。この場合は、結晶粒は立方体に近い形態であるが、頂点にあたるところ、即ち［１１１］方向が突き出しており、面にあたるところ、すなわち｛１００｝面は凹面になっていることがわかる。突き出しの先には、ほぼ三角形の小さい平面が存在する。これは、｛１１１｝面に相当する。
【００５５】
α≪１の例として、試料番号３及び１０の走査電子顕微鏡写真を夫々図６（ａ）及び（ｂ）に示す。明らかに［１１１］方位に突起ができ、｛１００｝面が凹面になっていることがわかる。そのメカニズムは、以下のようなものであると推定する。成長開始前のダイヤモンド粒子は、α≒１．５の結晶形態をしており、［１１１］方位には、｛１１１｝面が存在した。そして、この条件で成長させたとき、［１１１］方位の成長速度が極めて速い一方、［１００］方位の成長速度が遅いため，｛１１１｝面はそのまま成長し続け、｛１００｝面はそのまま取り残される。｛１１１｝面が成長して柱状突起を作ると、その突起の側面の結晶方位は｛１００｝面ではないため成長速度は速い。そこを基点に、元の｛１００｝面を四隅から囲っていくように層状に成長する結果、｛１００｝面が凹面になると考えられる。
【００５６】
この図３から明らかなように、α≦１のダイヤモンド（■）を合成できる範囲は、線分Ｌ１と線分Ｌ２との間の領域である。また、基板温度が１１００℃以上であると、ファセットの平坦性が著しく損なわれ、欠陥が多く入ってしまう。
【００５７】
このため、Ｔは線分Ｌ２より大きく、線分Ｌ１より小さいことが必要であり、また、Ｔは１１００未満であることが必要である。この条件を数式で表したものが、前記数式１乃至３である。よって、本発明においては、ダイヤモンドの合成条件を、数式１乃至３を満たすものとする。
【００５８】
なお、基板温度は２波長赤外線放出を検出して行う放射温度計により測定した値とすることができる。また、一時的であればダイヤモンド合成中にこの範囲を逸脱しても構わない。
【００５９】
このように構成された本実施形態においては、Ｔ＝３３５００×（ｙ−ｚ）／（ｘ＋Ｙ−ｚ）＋７１７は、ほぼα＝１の境界線を、Ｔ＝２５４０００×（ｙ−ｚ）／（ｘ＋ｙ−ｚ）＋７１７は、エッチングと成長の境界線を表し、またＴ≧１１００では、グラファイトが析出するなど、高品質なダイヤモンドが得られないので、上記数式１乃至３の条件でダイヤモンドを合成することにより、α≦１のダイヤモンドを効率よく合成することができる。
【００６０】
数式１乃至３を満足する条件範囲を、水素、メタン、二酸化炭素の混合ガスで実現できる。このガス種を使用することにより、数式１〜３を満足する条件は、総流量を現実的な値、例えば毎分１０リットル以下としつつ、各ガス流量を１ｓｃｃｍ（０℃１気圧換算で毎分１ｃｃの流量）以上に設定することができる。ガス流量を１ｓｃｃｍ以上にすることにより、反応ガス中の濃度制御が容易で、残留ガス、不純物及び反応容器内壁等の付着物の影響を少なくし、かつ高い再現性を確保できる。また、酸素源として二酸化炭素を使用することにより、高い安全性を確保できる。
【００６１】
数式１乃至３の範囲において、ガス種を水素、メタン及び二酸化炭素とすることは、特に５ｋＷ以上、望ましくは６０ｋＷ以上のマイクロ波プラズマＣＶＤ法を使用する場合に最適である。
【００６２】
公知文献３に示されている従来の合成条件は、１．５ｋＷ以下の装置を用いたものであり、これと５ｋＷ以上の装置とは明らかに条件範囲が異なっている。その理由を解明する一つの手がかりとして、プラズマ発光の違いが考えられる。即ち、約５ｋＷ以上のプラズマ発光とそれ未満のプラズマ発光を比較すると、約５ｋＷ以上のプラズマ発光の場合は水素のＨ_α線より炭素のＣ_２線の強度が高いことが大きな特徴である。本願発明者等は、先ず、６０ｋＷ装置で実施した結果をもとに本発明を完成したが、約５ｋＷ以上のプラズマ発光の場合はそれ未満のプラズマ発光の場合と異なり、炭素Ｃ_２線の強度が水素Ｈ_α線の強度より高くなることを考慮すると、水素のＨ_α線より炭素のＣ_２線の強度が高いプラズマを発生した場合に本発明を適用可能であるという考えに至る。即ち、炭素Ｃ_２強度が高いということは、メタン又は二酸化炭素など元のガスを効率よく分解し、反応した結果といえる。つまり、容器内に導入した水素、メタン、二酸化炭素の各分子には、炭素原子２個以上の結合は含まれていない。一方、プラズマ中に炭素原子２個の結合状態であるＣ_２が検出されたということは、即ち、メタン又は二酸化炭素の分子が分解された結果生ずる炭素原子が、新たに２個結合して生成したと考えられる。メタン又は二酸化炭素が分解されなければＣ_２が生成され得ないわけであるから、Ｃ_２のプラズマ発光が強いということは、メタン又は二酸化炭素が効率よく分解されていると結論付けられる。従って、装置又はガスの分解方法が異なっても、例えば、５ｋＷマイクロ波プラズマを使用した合成装置のように、ガスを効率よく分解、反応させることができる方法であれば、ここで示した条件範囲を適用できると考えられる。
【００６３】
比較のために、図１に示すものと同じ装置で、メタンと水素のみを反応ガスとして使用してダイヤモンドを合成した結果について、図７に示す。図７は横軸に有効炭素濃度ｃをとり、縦軸に基板温度をとって、両者の関係を示すグラフ図である。この比較例のように、酸素原子を含むガスを使用していない場合、α＝１．２程度までが限界で、α≦１となる実験条件を見出すことができない。有効炭素濃度ｃ＝０、即ち水素１００％の場合、ダイヤモンドは確かにエッチングされるが，その量はごく僅かで、１０ｎｍ／時以下であった。また、ダイヤモンドを高速にエッチングするには、ｃ＜０にすればよいと推測できる。しかしながら、メタンと水素のみでは、酸素原子を含まないのでｃ＜０にできない。従って、メタンと水素のみではエッチング目的には不適である。
【００６４】
次に、結晶方位と成長速度との関係について説明する。結晶方位［１１１］及び［１００］の方向への成長速度を夫々Ｖ［１１１］及びＶ［１００］とするとき、Ｖ［１００］／Ｖ［１１１］＜１／√３とすることが好ましい。
【００６５】
この範囲の結晶成長速度比は、前述の数式１乃至３の条件、ガス種、及びマイクロ波出力の範囲を満足することにより、得ることができる。その結果、得られたダイヤモンドの結晶方位は［１１１］が支配的となり、［１１１］配向膜を確実に得ることができる。
【００６６】
数式１乃至３を満足する条件で合成されたダイヤモンドは、図５に示すように、α≦１となり、その結晶形状は、［１００］方位に凹面を有するか、［１１１］方位に突起を有するか、又はその双方を示す結晶形状となる。
【００６７】
このような結晶形状を有するダイヤモンドを合成することにより、［１１１］配向膜をさらに高効率に得ることができる。また、多くの柱状突起を上面に形成することもでき、低反射面、電子放出面、フォトニック面、又は広い表面積が望まれるガスセンサ、吸着面、触媒反応面，電極等にも応用可能となる。更に、柱状突起ができる条件（α≦１）で所望の膜厚まで成長させ、その後成長条件をα＞１に変え、所望の表面形態、例えば｛１１１｝の平坦面などを得ることも可能である。
【００６８】
従来のダイヤモンド成長条件では、ダイヤモンド結晶は実質的に｛１００｝面と｛１１１｝面で構成された正八面体、立方体又はその中間であるいわゆる六八面体を基本としている。そのため、アスペクト比（断面の径又は幅に対する長さの比）が大きい柱状の結晶は得られなかった。凸部の形状は、最も鋭いもので正八面体の頂点である。柱形状を得るためには、ダイヤモンドを成長させた後、残したい部分をマスクし、他をエッチングする等の方法によらなければならない。しかしながら、本発明によれば、α＜１の条件を用いることにより、成長のみで柱形状を得ることが可能となる。
【００６９】
柱状結晶は、光を照射したときには多重反射を効果的にさせやすく、電界を印加したときには先端に電界を集中させやすく、単位投影面積あたりの表面積を増大する効果があることが一般的に知られている。従って、柱状結晶が望まれる用途、例えば、低反射面、電子放出面、フォトニック面、又は広い表面積が望まれるガスセンサ、吸着面、触媒反応面、電極等にダイヤモンドを応用する際、本発明によれば、ダイヤモンド成長と同時に柱状結晶が得られるので便利である。
【００７０】
上記の柱状結晶は、結晶方位によらず有効な場合もあるが、柱頂面が｛１１１｝面であることにより特別の効果が発揮できる場合がある。例えば、｛１１１｝面を保ちながら結晶成長させると、｛１００｝面の場合より不純物を取り込まれやすいことが知られている。ダイヤモンド中に取り込まれる不純物としては、窒素、ホウ素、リン、硫黄、ニッケルなどが代表的であり、それぞれを意図的にドーピングした場合の機能は既知である。これらの機能を付加するため、本発明によればダイヤモンド成長時に効率よくドーピングすることができる。
【００７１】
また、ドーピング時の効果とは別に、｛１１１｝面はダイヤモンドの最も硬い面であることから、機械的強度を求められる用途にも本発明は有効である。最表面を｛１１１｝面にすることにより、耐摩耗性が向上することは既知である。本発明によれば、ダイヤモンドを［１１１］配向成長させ、最表面を｛１１１｝面で簡単に覆うことができる。
【００７２】
上述のように、本発明により製造されたダイヤモンドは、耐摩耗材料、装飾材料及びそのコーティング、化学反応用電極等の各種電極、ヒートシンク、表面弾性波素子、電子放出材料、Ｘ線窓、光学関連材料、又はトランジスタ、ダイオード、各種センサ等の電子装置等に使用することができる。
【００７３】
【発明の効果】
以上詳述したように、本発明によれば、結晶形態を表すαパラメータが１以下であるダイヤモンドを高効率で製造することができる。
【図面の簡単な説明】
【図１】出力６０ｋＷ、周波数９１５ＭＨｚマイクロ波プラズマＣＶＤ装置（ΑＳＴｅＸ／セキテクノトロン社製）を示す模式図である。
【図２】（ａ）及び（ｂ）は、夫々有効炭素濃度ｃが０（ＣＯ_２／ＣＨ_４＝１．０）の場合のプラズマ曝露（成長）前及び追成長後のダイヤモンド粒子の変化を示す走査型電子顕微鏡写真である。
【図３】有効炭素濃度ｃ（％）と基板温度Ｔ（℃）とから決まる領域と、αパラメータとの関係を示すグラフ図である。
【図４】α≒１のダイヤモンド結晶を示す走査型電子顕微鏡写真である。
【図５】α＜１のダイヤモンド結晶を示す走査型電子顕微鏡写真である。
【図６】α≪１で［１１１］方向の突起が顕著になったダイヤモンド結晶を示す走査型電子顕微鏡写真である。
【図７】原料ガスがメタン及び水素のみの場合において、有効炭素濃度ｃ（％）及び基板温度Ｔ（℃）とαパラメータとの関係を示すグラフ図である。
【符号の説明】
１：反応容器
２：蓋
３：底部
４：マイクロ波導入部
５：基板支持台
６：基板
７：原料ガス入口
８：マイクロ波出口窓
９：排気管
１０：冷却水導入管[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides wear-resistant materials, decorative materials and their coatings, various electrodes such as electrodes for chemical reactions, heat sinks, surface acoustic wave devices, electron-emitting materials, X-ray windows, optical-related materials, transistors, diodes, various sensors, and the like. The present invention relates to a method for producing a vapor-phase synthetic diamond used for an electronic device and the like and a diamond product.
[0002]
[Prior art]
Diamond is the hardest among materials, has excellent heat resistance, has a large band gap of 5.47 eV, and is usually an insulator, but has a characteristic that it can be made into a semiconductor by impurity doping. In addition, diamond has excellent electrical characteristics such as a high dielectric breakdown voltage and a high saturation drift velocity, and a low dielectric constant. Due to such characteristics, diamond is expected as an electronic device / sensor material for high temperature, high frequency, and high electric field, as well as a wear resistant coating of a tool.
[0003]
In addition, application to photosensors and light-emitting elements corresponding to short wavelength regions such as ultraviolet rays utilizing the large band gap of diamond, heat dissipation substrate materials and materials utilizing the large thermal conductivity and small specific heat Applications to surface acoustic wave devices utilizing the property of being the hardest, applications to X-ray windows or optical materials utilizing high light transmittance and refractive index, etc. are being promoted. In addition, diamond is used in wear-resistant members of tools.
[0004]
In addition, diamond is not corroded by acids and alkalis, is extremely stable chemically, and has conductivity by being doped with boron, and is considered to be promising as an electrode for chemical reactions. ing.
[0005]
As a method for synthesizing a diamond film in a gas phase, a microwave chemical vapor deposition (CVD) method (for example, JP-B-59-27754 and JP-B-61-3320), a high-frequency plasma CVD method, and a hot filament CVD method Gas phase synthesis methods such as direct current plasma CVD, plasma jet, combustion flame, and thermal CVD are known.
[0006]
In the above-mentioned gas phase synthesis, a hydrocarbon or carbon monoxide such as methane, ethane, alcohol, or acetylene is used as a raw material, and a mixed gas obtained by diluting the raw material with a hydrogen gas is often used as a reaction gas.
[0007]
By the way, well-known documents 1 (Watanabe, Takeuchi, Yamanaka, Sekiguchi, Ogushi, Kajimura: Abstracts of the 13th Diamond Symposium (Waseda Univ., 1999) P.10) and well-known documents 2 (Watanabe, Ohgushi: 14th Diamond) A summary of the symposium (Otsukuba Institute of Industrial Science, 2000) Abstracts P. 154) proposes a method of synthesizing a high-quality diamond thin film with an extremely low methane concentration of 0.05% or less. In this case, a single crystal diamond (100) plane is used as a substrate, and an atomic layer size step flow growth is realized thereon to achieve high quality.
[0008]
Atomic level planarization is also performed by exposing the diamond surface to plasma of 100% hydrogen and performing anisotropic etching depending on the crystal plane.
(Addition of oxygen-containing gas)
In some cases, a reaction gas to which oxygen, carbon dioxide, water vapor, or the like is added in addition to the above reaction gas is used. In this case, it is considered that only high-quality diamond can be grown because oxygen atoms have an effect of strongly suppressing precipitation of non-diamond components and diamond having many crystal defects. When the ratio of oxygen atoms in the reaction gas is large, the growth of high-quality diamond is also suppressed. When the oxygen atoms are above a certain ratio, diamond does not grow at all and is conversely etched.
[0009]
Conventionally, the ratio of oxygen atoms at the boundary between the growth and the etching can be considered as the ratio to carbon atoms in the reaction gas. When the value of oxygen atoms / carbon atoms is around 1, diamond can grow, exceeding 1 In this case, if it exceeds 2, for example, the diamond does not grow, but rather the etching proceeds. As a typical example, it is well known that diamond can be synthesized when carbon monoxide + hydrogen is used as a reaction gas. On the other hand, there is no report that diamond is grown using carbon dioxide + hydrogen, and it is rather known that diamond is etched.
[0010]
Conditions for synthesizing diamond are disclosed in a known document 3 (P. Koidl, C. Wild, and N. Herres: Proc. NIRIM Int'l. Symp. Advanced Materials '94, Tsukuba (Japan), March 13-17, 1994, p. 1)) and the like, the distribution of the “α parameter” representing the crystal form with respect to the methane concentration and the substrate temperature is described. The α parameter refers to the lamination speed of the crystal planes {111} and {100} as V ₁₁₁ And V ₁₀₀ Where α = √3 × V ₁₀₀ / V ₁₁₁ Is defined by In the case of diamond, it is known that the facets that appear as a result of crystal growth are mainly {111} planes and {100} planes, and slightly {110} planes and {311} planes may appear. In most cases, the crystal form can be expressed by the appearance of the {111} plane and the {100} plane. Therefore, when the crystal growth starts from a minute nucleus, it can be said that the α parameter represents the crystal form that appears as a result of the growth. A crystal form corresponding to a typical α parameter is disclosed in a known document 4 (C. Wild, P. Koidl, W. Muller-Sebert, H. Walcher, R. Kohl, N. Herres, R. Locher, R. Samlenski, and R, Brenn: Diamond Relat, Mater., 2 (1993) 158). When α = 1, all surfaces are cubes consisting of {100} surfaces, but in the middle, {111} surfaces appear as if the vertices of the cubes were cut off, and {111} as the α value increases. The {plane} is large and the {100} plane is small. When α = 3, the {100} face disappears, and all the faces are covered with the {111} face, forming a regular octahedron.
[0011]
In the known document 3, the condition area having a small α value is clearly indicated up to the line of α = 1.5, but there is no line of α = 1, and the line is not actually implemented. At least, the conditions that can be obtained stably in a controllable range are not the reaction gas system of methane and hydrogen, and there is no example implemented so far when α <1.
[0012]
In the well-known document 5 (Yokota, Ando, Watanabe, Nishibayashi, Kobashi, Hirao, Oyo: The 15th Diamond Symposium (at Tokyo Institute of Technology, 2001) Abstract Proceedings P.4), use the synthesis condition of α = 3. Thus, an example in which a [100] -oriented polycrystalline diamond is grown has been reported. This is considered as the following mechanism. When α = 3, the growth rate in the [100] direction is faster than the growth rate in the [111] direction. On the other hand, when growing a polycrystalline film on a substrate, the initial diamond growth nuclei are oriented in random directions. These become continuous films as they grow, but the crystal with the higher growth rate oriented upwards naturally grows faster and eventually covers the crystals oriented in other directions. I will. As a result, only crystals oriented in a specific direction appear on the surface, and a so-called alignment film is obtained.
[0013]
[100] When forming an alignment film, it is effective to use the condition of α ≧ 3. However, since the facets appearing at this time are regular octahedral with {111} planes, the pyramids are pointed at the top. It becomes a surface morphology in which crystal-like crystals gather. If a flat surface of [100] orientation is to be used, the top of the pyramid-shaped crystal is polished or changed to a condition close to α = 1 so that the {100} plane is expanded. It is necessary to perform additional growth (change the conditions and restart diamond growth).
[0014]
[Problems to be solved by the invention]
However, usually, the residual gas and impurities generated due to incomplete vacuuming before the reaction are mixed in the reaction gas, and even if these residual gases and impurities are small, the carbon concentration in the reaction gas is extremely low. Therefore, the amount becomes relatively nonnegligible. Further, it is considered that a high-quality diamond can be synthesized by lowering the growth rate as much as possible, and a method of making the methane concentration extremely low, such as the above-mentioned methane concentration of 0.025%, is possible. It is extremely difficult to control the gas concentration, and the reproducibility seems to be difficult.
[0015]
One of the reasons is as follows. With the synthesis of diamond, non-diamond carbon is also likely to precipitate on the inner surface of the reaction vessel, but this is taken into the reaction gas when the next synthesis is started. Therefore, even if the gas introduced into the reaction vessel is accurately controlled, it is extremely difficult to control the carbon concentration in the plasma after all because of the contamination of the carbon adhering to the inner surface of the reaction vessel.
[0016]
When the reaction gas is 100% hydrogen, non-diamond carbon is easily etched, and even diamond is etched at a relatively low etching rate. It is thought that if a little methane is mixed in the reaction gas, diamond will not be etched and growth will start.However, the conditions near the boundary between etching and growth depend on the surface modification and surface orientation of diamond and the start of etching or growth. It is considered that selective etching and selective growth can be realized by the difference in concentration.
[0017]
However, in the methane + hydrogen system, such boundary conditions are virtually unfeasible. Therefore, a method of adding an oxygen-containing gas is conceivable, but the amount of addition has been considered to be suitable for diamond growth when C / O = 1 as described above. However, the present inventors have found that in a device using a high-power microwave, when C / O = 1, diamond is clearly etched rather than grown. That is, it was found that it is necessary to individually determine the amount of the oxygen-containing gas to be added depending on the apparatus or the synthesis method.
[0018]
As an oxygen source, oxygen, water vapor, and the like are used in addition to carbon dioxide. Oxygen has a risk of explosion due to mixing with hydrogen depending on the concentration and pressure conditions. Since water vapor is a liquid at normal temperature and normal pressure, a device for gasifying by bubbling or the like must be added.
[0019]
In the prior art, the condition of α <1 is not implemented. In particular, in the methane + hydrogen system, the condition of α <1.2 is considered to be at an extremely high temperature and a low methane concentration, but the realization is performed on the apparatus. It is extremely difficult due to restrictions and deformation of the substrate.
[0020]
As described above, for example, when it is desired to form a [100] alignment film, the formation may be performed under the condition of α ≧ 3. On the other hand, in order to efficiently produce the [111] orientation film, it is considered that it is desirable to perform the process under the condition of α ≦ 1. However, conventionally, the condition of α ≦ 1 cannot be realized in the first place.
[0021]
The present invention has been made in view of such a problem, and a method for producing a diamond and a diamond product capable of efficiently synthesizing a diamond of α ≦ 1 by using an oxygen-containing gas such as carbon dioxide. The purpose is to provide.
[0022]
[Means for Solving the Problems]
In the method for producing diamond according to the present invention, the ratio of the number of hydrogen atoms in the reaction gas is 2x (%), the ratio of the number of carbon atoms is y (%), the ratio of the number of oxygen atoms is z (%), and the substrate temperature is T ( C), diamond is vapor-phase synthesized under the conditions shown in the following formulas 1 to 3.
[0023]
(Equation 1)
T> 33500 × (yz) / (x + yz) +717
[0024]
(Equation 2)
T <254000 × (yz) / (x + yz) +717
[0025]
[Equation 3]
T <1100
[0026]
In the method for producing diamond, the reaction gas includes, for example, hydrogen, methane, and carbon dioxide.
[0027]
Also, the reaction gas can be put into a plasma state by a microwave of 5 kW or more to synthesize diamond in a gas phase.
[0028]
Furthermore, when the growth rates in the directions of the crystal orientations [111] and [100] are V [111] and V [100], respectively, V [100] / V [111] <1 / √3. preferable.
[0029]
Further, it is preferable to produce diamond having a crystal shape having a concave surface of [100] orientation and / or a projection of [111] orientation.
[0030]
Furthermore, after a diamond having a crystal shape having a concave surface in the [100] direction and / or a protrusion in the [111] direction is once formed, the diamond can be further grown and grown.
[0031]
The diamond product according to the present invention is characterized by using diamond produced by the method for producing diamond according to the present invention.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a microwave plasma CVD apparatus used in the embodiment of the present invention. A lid 2 is arranged on the bottom 3 of the reaction vessel 1 so that the inside is airtightly isolated. From the center of the bottom 3, for example, a microwave having a frequency of 915 MHz and an output of 60 kW is introduced into the reaction vessel 1 via the microwave introduction unit 4. A substrate support 5 placed on the bottom 3 via a spacer is installed inside the reaction vessel immediately above the microwave introduction unit 4. A substrate 6 on which diamond is to be synthesized is placed on the substrate support 5. The lid 2 is provided with a source gas inlet 7, and a slight gap is provided between the substrate support table 5 and the bottom 3 by the spacer, and the gap serves as a microwave exit window 8. An exhaust pipe 9 is connected to the bottom 3 so as to exhaust the inside of the reaction vessel 1, and further, an introduction for introducing cooling water to the substrate support 5 at the center of the microwave introduction section 4. A tube 10 is provided. The substrate support 5 is cooled by the cooling water supplied by the cooling water introduction pipe 10. As such a microwave plasma CVD apparatus, there is an apparatus manufactured by STex / Seki Technotron.
[0033]
In this microwave plasma CVD apparatus, the substrate 6 is placed on the substrate support 5, and cooling water is supplied to the substrate support 5 via the introduction pipe 10 to cool the same. The inside of the reaction vessel 1 is evacuated by a vacuum pump, and the material gas is introduced into the reaction vessel 1 from the material gas inlet 7 while continuing the evacuation, and the microwave (915 MHz, 60 kW) is reacted from the introduction part 4. It is introduced into the container 1. As a result, a plasma 11 is generated above the substrate 6, and the plasma 11 causes diamond to grow on the substrate.
[0034]
Next, a method for producing a diamond according to an embodiment of the present invention will be described. In the present embodiment, the ratio of the number of hydrogen atoms in the reaction gas is 2x (%), the ratio of the number of carbon atoms is y (%), the ratio of the number of oxygen atoms is z (%), and the substrate temperature is T (° C). At this time, diamond is vapor-phase synthesized under the conditions shown in the above formulas 1 to 3.
Examples of such a reaction gas include those containing hydrogen, methane, and carbon dioxide.
[0035]
Also, the reaction gas can be put into a plasma state by a microwave of 5 kW or more to synthesize diamond in a gas phase.
[0036]
Furthermore, when the growth rates in the directions of the crystal orientations [111] and [100] are V [111] and V [100], respectively, V [100] / V [111] <1 / √3. preferable.
[0037]
Further, it is preferable to produce diamond having a crystal shape having a concave surface of [100] orientation and / or a projection of [111] orientation.
[0038]
Furthermore, after a diamond having a crystal shape having a concave surface in the [100] direction and / or a protrusion in the [111] direction is once formed, the diamond can be further grown.
[0039]
Thus, a silicon wafer was used as the substrate 6, the upper surface of which was scratched with diamond powder, and the one on which diamond particles were grown to 1 to several μm in advance to synthesize diamond. Tried. The change in the shape of the diamond particles before and after the synthesis was measured from a scanning electron microscope photograph, the value of the α parameter was calculated, or it was determined whether the diamond particles on the silicon substrate 6 were etched. Table 1 shows the synthesis (film formation) conditions, the results of the synthesis, and the α values.
[0040]
[Table 1]

[0041]
Next, two methods for calculating the α value will be described. First, the first method is as follows.
1) After scratching the surface of the substrate (scratching), diamond crystal particles of 1 to several μm were previously grown on the substrate. The growth conditions at this time were set so that both the {100} plane and the {111} plane clearly appeared in order to easily obtain the growth rate in 3) below. That is, growth conditions corresponding to α = about 1.5 to 2 were used. 2) Next, the size of the diamond crystal grains in which both the {100} plane and the {111} plane appeared were measured. Specifically, the length of the edge of each crystal plane was measured by observation with an electron microscope, and since the relative angle of each crystal plane was known crystallographically, the shape and size of the crystal particles were determined. Note that, as the crystal particles to be measured, those in which two or more crystal particles were not in close proximity were selected. If the crystal grains come into contact during the growth, no further growth can be performed on the contact surface side, so that an accurate growth amount cannot be measured.
3) Next, the crystal grains were grown as seeds under each condition for 1 to 2 hours.
4) The shape and size of the crystal after growth were determined in the same manner as in 2).
5) The shapes and sizes of the crystal grains obtained in 2) and 4) were compared, and the amount of the crystal grains grown in the [100] direction and the [111] direction was geometrically calculated. The growth rate was normalized by the growth time, and the growth rate was determined. When the crystal particles do not grow and become smaller, the diamond particles have been etched by the plasma exposure. At this time, the growth amount and the growth rate have negative values. The [100] direction and the [111] direction correspond to the normal direction of the {100} plane and the normal direction of the {111} plane, respectively.
[0042]
Next, a second method for calculating the α parameter will be described.
1) After the substrate surface was scratched (scratched), diamond was grown directly to several μm under each condition. At this time, the size of the crystal grains before growth can be regarded as zero. However, the scratching process causes a small scratch on the substrate (silicon in the embodiment), and diamond growth starts from the scratch. On the other hand, since the scratch treatment is usually performed with diamond powder, the fragments may remain on the substrate and grow as seeds. However, since the fragment is almost 0.1 μm or less in most cases, the initial value can be considered to be substantially zero in any case if the growth is performed for several μm.
2) The shape and size of the crystal grains were determined in the same manner as in 2) of the first method.
3) Geometrically, the growth amounts in the [100] and [111] directions were calculated, normalized by the growth time, and the growth rate was obtained.
[0043]
Note that the second method can be used only when the value of the α parameter is more than 1 and less than 3, that is, when both the {100} plane and the {111} plane appear. However, since the values of α ≦ 1 and α ≧ 3 cannot be determined in the second method, the first method should be used.
[0044]
However, only in Table 1, sample numbers 24 to 28, diamond was grown according to the second method, and a crystal covered only with the {111} plane was obtained. α ≧ 3.
[0045]
As shown in Table 1, depending on the synthesis conditions, the diamond particles were etched and reduced in size. FIGS. 2A and 2B respectively show an effective carbon concentration of 0 (CO 2). ₂ / CH ₄ = 1.0) is a photograph taken by a scanning electron microscope of the shape of diamond particles on the substrate surface before and after plasma exposure. FIG. 2 (a) shows diamond particles before growth, and FIG. 2 (b) shows diamond particles after additional growth and after etching. As shown in FIGS. 2A and 2B, the diamond particles are etched and reduced by the additional growth.
[0046]
The “effective carbon concentration” is defined as the following formula, where the ratio of the number of hydrogen atoms in the reaction gas is 2x (%), the ratio of the number of carbon atoms is y (%), and the ratio of the number of oxygen atoms is z (%). 4 means c.
[0047]
(Equation 4)
c = (yz) / (x + yz) × 100 (%)
[0048]
This effective carbon concentration cancels out oxygen atoms and carbon atoms in the reaction gas, and indicates a virtual partial pressure ratio between surplus carbon atoms and hydrogen molecules. Assuming that the expressed effective carbon concentration c represents the carbon concentration contributing to diamond growth, it has been found that the correlation can be expressed by classifying the synthesis conditions and the synthesis results.
[0049]
FIG. 3 is a graph showing the relationship between the effective carbon concentration c (%) on the horizontal axis and the substrate temperature T (° C.) on the vertical axis. In the figure, x indicates the experimental conditions under which the diamond did not grow and the diamond was etched. In addition, Δ indicates the experimental conditions when α ≦ 1, ● indicates 1 <α <3, and Δ indicates the experimental conditions when α ≧ 3. As shown in FIG. 3, as a result, the vicinity of the line segment L1 (solid line) is the boundary between etching and growth, the vicinity of the line segment L2 (dashed line) is α = 1, and the vicinity of the line segment L3 (solid curve). Becomes α = 3. When these line segments are represented by mathematical expressions, the following mathematical expressions 5 to 7 are obtained.
[0050]
(Equation 5)
Line segment L1: T = 2540c + 717: boundary between etching and growth
[0051]
(Equation 6)
Line segment L2: T = 335c + 717: α = 1
[0052]
(Equation 7)
Line segment L3: T = 89Ln (c) +869: α = 3 (Ln is a natural logarithm)
[0053]
As examples of α ≒ 1, scanning electron micrographs of Sample Nos. 5 and 11 are shown in FIGS. 4A and 4B, respectively. In FIG. 4 (a), α = 1 almost exactly, and although twin aggregates are observed, crystals having only square {100} planes are all grown. As can be seen from some of them, those without twins are cubes. In FIG. 4B, an extremely small regular triangle {111} plane is observed at the vertex of the cube, and the α value is slightly deviated from 1.
[0054]
As examples of α <1, scanning electron micrographs of sample numbers 6 and 9 are shown in FIGS. 5A and 5B, respectively. In this case, the crystal grains have a form close to a cube, but it can be seen that the apex, that is, the [111] direction protrudes, and the part corresponding to the plane, that is, the {100} plane is concave. At the end of the protrusion, there is a small plane that is substantially triangular. This corresponds to the {111} plane.
[0055]
As examples of α≪1, scanning electron micrographs of Sample Nos. 3 and 10 are shown in FIGS. 6A and 6B, respectively. It can be seen that a projection is clearly formed in the [111] direction, and the {100} plane is concave. The mechanism is presumed to be as follows. The diamond particles before the start of growth had a crystal form of α ≒ 1.5, and had a {111} plane in the [111] orientation. When grown under these conditions, the growth rate in the [111] direction is extremely high, while the growth rate in the [100] direction is low, so that the {111} plane continues to grow and the {100} plane is left untouched. It is. When the {111} plane grows to form columnar projections, the crystal orientation on the side surfaces of the projections is not a {100} plane, so the growth rate is high. It is thought that the {100} plane becomes concave as a result of growing in layers from the four corners around the original {100} plane.
[0056]
As is apparent from FIG. 3, the range in which diamond (■) with α ≦ 1 can be synthesized is a region between the line segment L1 and the line segment L2. On the other hand, when the substrate temperature is 1100 ° C. or higher, the flatness of the facet is significantly impaired, resulting in many defects.
[0057]
Therefore, T needs to be larger than the line segment L2 and smaller than the line segment L1, and T needs to be smaller than 1100. Equations 1 to 3 express this condition in mathematical expressions. Therefore, in the present invention, it is assumed that the conditions for synthesizing diamond satisfy Expressions 1 to 3.
[0058]
The substrate temperature can be a value measured by a radiation thermometer which detects and emits two-wavelength infrared rays. If it is temporary, it may be outside this range during diamond synthesis.
[0059]
In the present embodiment configured as above, T = 33500 × (yz) / (x + Y−z) +717 is substantially equal to the boundary of α = 1, and T = 254000 × (yz) / ( (x + yz) +717 represents a boundary between etching and growth. When T ≧ 1100, high-quality diamond cannot be obtained, such as precipitation of graphite. Thereby, diamond with α ≦ 1 can be efficiently synthesized.
[0060]
The condition range satisfying the formulas 1 to 3 can be realized with a mixed gas of hydrogen, methane, and carbon dioxide. By using this gas type, the condition satisfying the formulas 1 to 3 is that the total flow rate is set to a realistic value, for example, 10 liters / minute or less, and each gas flow rate is set to 1 sccm (0 ° C./atm. (1 cc flow rate) or more. By controlling the gas flow rate to 1 sccm or more, it is easy to control the concentration in the reaction gas, to reduce the influence of residual gas, impurities and deposits on the inner wall of the reaction vessel, and to ensure high reproducibility. In addition, by using carbon dioxide as an oxygen source, high safety can be ensured.
[0061]
The use of hydrogen, methane and carbon dioxide as the gas species in the range of Expressions 1 to 3 is most suitable when using a microwave plasma CVD method of 5 kW or more, preferably 60 kW or more.
[0062]
The conventional synthesis condition shown in the known document 3 uses an apparatus of 1.5 kW or less, and the condition range is clearly different from that of the apparatus of 5 kW or more. One clue to elucidate the reason is the difference in plasma emission. That is, comparing the plasma emission of about 5 kW or more with the plasma emission of less than about 5 kW, when the plasma emission of about 5 kW or more, the hydrogen H _α Carbon from the line ₂ A great feature is that the strength of the line is high. The present inventors first completed the present invention based on the results obtained by using a 60 kW apparatus. However, in the case of plasma emission of about 5 kW or more, unlike the case of plasma emission of less than about 5 kW, the carbon C ₂ The intensity of the line is hydrogen H _α Considering that the intensity becomes higher than that of the line, the hydrogen H _α Carbon from the line ₂ This leads to the idea that the present invention can be applied to a case where a plasma having a high line intensity is generated. That is, carbon C ₂ High strength means that the original gas such as methane or carbon dioxide is efficiently decomposed and reacted. That is, each of the molecules of hydrogen, methane, and carbon dioxide introduced into the container does not contain a bond having two or more carbon atoms. On the other hand, in the plasma, C ₂ Is detected, that is, it is considered that two carbon atoms generated as a result of the decomposition of methane or carbon dioxide molecules are newly bonded. If methane or carbon dioxide is not decomposed, C ₂ Cannot be generated, so C ₂ It is concluded that methane or carbon dioxide is efficiently decomposed when the plasma emission of the compound is strong. Therefore, even if the method of decomposing the gas or the apparatus is different, if the method is such that the gas can be decomposed and reacted efficiently, for example, as in a synthesis apparatus using 5 kW microwave plasma, the condition range shown here It is considered that can be applied.
[0063]
For comparison, FIG. 7 shows a result of synthesizing diamond using the same apparatus as that shown in FIG. 1 and using only methane and hydrogen as reaction gases. FIG. 7 is a graph showing the relationship between the effective carbon concentration c on the horizontal axis and the substrate temperature on the vertical axis. When a gas containing an oxygen atom is not used as in this comparative example, the limit is up to about α = 1.2, and no experimental conditions satisfying α ≦ 1 can be found. When the effective carbon concentration is c = 0, that is, when the hydrogen concentration is 100%, the diamond is certainly etched, but the amount is very small, that is, less than 10 nm / hour. Also, it can be assumed that c <0 should be satisfied in order to etch diamond at high speed. However, methane and hydrogen alone do not contain oxygen atoms and cannot be set to c <0. Therefore, methane and hydrogen alone are not suitable for etching purposes.
[0064]
Next, the relationship between the crystal orientation and the growth rate will be described. When the growth rates in the directions of the crystal orientations [111] and [100] are V [111] and V [100], respectively, it is preferable that V [100] / V [111] <1 / √3.
[0065]
The crystal growth rate ratio in this range can be obtained by satisfying the above-described conditions of Expressions 1 to 3, the gas type, and the range of the microwave output. As a result, the crystal orientation of the obtained diamond is [111] dominant, and the [111] oriented film can be reliably obtained.
[0066]
As shown in FIG. 5, the diamond synthesized under the conditions satisfying Expressions 1 to 3 has α ≦ 1, and its crystal shape has a concave surface in the [100] direction or a projection in the [111] direction. Or a crystal shape showing both of them.
[0067]
By synthesizing diamond having such a crystal shape, a [111] -oriented film can be obtained with higher efficiency. In addition, many columnar projections can be formed on the upper surface, and can be applied to a low reflection surface, an electron emission surface, a photonic surface, or a gas sensor, an adsorption surface, a catalytic reaction surface, an electrode, or the like where a large surface area is desired. . Furthermore, it is also possible to grow to a desired film thickness under conditions (α ≦ 1) where columnar projections can be formed, and then change the growth condition to α> 1, to obtain a desired surface morphology, for example, a {111} flat surface. is there.
[0068]
Under conventional diamond growth conditions, a diamond crystal is based on a regular octahedron substantially consisting of {100} planes and {111} planes, a cube, or a so-called hexahedron intermediate between them. Therefore, a columnar crystal having a large aspect ratio (ratio of length to cross-sectional diameter or width) could not be obtained. The shape of the projection is the sharpest one, which is the vertex of the octahedron. In order to obtain a columnar shape, it is necessary to use a method of growing a diamond, masking a portion to be left, and etching other portions. However, according to the present invention, by using the condition of α <1, it becomes possible to obtain a columnar shape only by growth.
[0069]
It is generally known that columnar crystals can easily make multiple reflections effective when illuminating light, easily concentrate electric fields at the tip when an electric field is applied, and have the effect of increasing the surface area per unit projected area. ing. Therefore, in applications where a columnar crystal is desired, for example, a low reflection surface, an electron emission surface, a photonic surface, or a gas sensor where a large surface area is desired, an adsorption surface, a catalytic reaction surface, and the like, when diamond is applied to the present invention, According to this, a columnar crystal can be obtained simultaneously with the growth of diamond, which is convenient.
[0070]
The above-mentioned columnar crystal is effective in some cases regardless of the crystal orientation, but a special effect may be exerted when the column top surface is a {111} plane. For example, it is known that when the crystal is grown while maintaining the {111} plane, impurities are more easily taken in than in the case of the {100} plane. Typical examples of impurities taken into diamond include nitrogen, boron, phosphorus, sulfur, nickel, and the like, and the functions when intentionally doped with each are known. In order to add these functions, according to the present invention, doping can be efficiently performed during diamond growth.
[0071]
In addition to the effect at the time of doping, the {111} plane is the hardest surface of diamond, so that the present invention is also effective for applications requiring mechanical strength. It is known that the wear resistance is improved by setting the outermost surface to the {111} plane. According to the present invention, diamond can be grown with [111] orientation and the outermost surface can be easily covered with {111} planes.
[0072]
As described above, the diamond manufactured according to the present invention can be used for abrasion-resistant materials, decorative materials and their coatings, various electrodes such as electrodes for chemical reaction, heat sinks, surface acoustic wave devices, electron-emitting materials, X-ray windows, and optical-related materials. The material can be used for electronic devices such as transistors, diodes, and various sensors.
[0073]
【The invention's effect】
As described in detail above, according to the present invention, diamond having an α parameter representing a crystal form of 1 or less can be manufactured with high efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a microwave plasma CVD apparatus (@ STeX / Seki Technotron Co., Ltd.) with an output of 60 kW and a frequency of 915 MHz.
FIGS. 2 (a) and (b) show that the effective carbon concentration c is 0 (CO ₂ / CH ₄ = 1.0) is a scanning electron micrograph showing changes in diamond particles before plasma exposure (growth) and after additional growth in the case of (1.0).
FIG. 3 is a graph showing a relationship between a region determined by an effective carbon concentration c (%) and a substrate temperature T (° C.) and an α parameter.
FIG. 4 is a scanning electron micrograph showing a diamond crystal having α ≒ 1.
FIG. 5 is a scanning electron micrograph showing a diamond crystal with α <1.
FIG. 6 is a scanning electron micrograph showing a diamond crystal in which protrusions in the [111] direction become prominent at α≪1.
FIG. 7 is a graph showing the relationship between the α parameter and the effective carbon concentration c (%) and the substrate temperature T (° C.) when the source gas is only methane and hydrogen.
[Explanation of symbols]
1: reaction vessel
2: lid
3: bottom
4: Microwave introduction part
5: Board support
6: Substrate
7: Source gas inlet
8: Microwave exit window
9: Exhaust pipe
10: Cooling water introduction pipe

Claims (7)

When the ratio of the number of hydrogen atoms in the reaction gas is 2x (%), the ratio of the number of carbon atoms is y (%), the ratio of the number of oxygen atoms is z (%), and the substrate temperature is T (° C), the following formula is used. A method for producing diamond, characterized in that diamond is vapor-phase synthesized under conditions.
T> 33500 × (yz) / (x + yz) +717
T <254000 × (yz) / (x + yz) +717
T <1100 The method of claim 1, wherein the reaction gas includes hydrogen, methane, and carbon dioxide. The method for producing diamond according to claim 1 or 2, wherein the reaction gas is made into a plasma state by microwaves of 5 kW or more to make diamond in a gas phase. When the growth rates in the directions of crystal orientations [111] and [100] are V [111] and V [100], respectively, V [100] / V [111] <1 / √3. The method for producing a diamond according to any one of claims 1 to 3. The method for producing diamond according to any one of claims 1 to 4, wherein diamond having a crystal shape having a concave surface having a [100] orientation and / or a projection having a [111] orientation is produced. The diamond according to any one of claims 1 to 4, wherein a diamond having a crystal shape having a concave surface having a [100] orientation and / or a projection having a [111] orientation is formed once, and then the diamond is further grown. Diamond production method. A diamond product using a diamond manufactured by the manufacturing method according to any one of claims 1 to 6.

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