半导体与宝石

 (1)半导体与晶体

历史上，半导体因晶体管的发明而名声雀起。但是半导体并不都是晶体。

周知，材料分为晶体和非晶体两大类。

晶体（ crystal ）是内部质点在三维空间成周期性重复排列的固体；或者说，晶体是具有格子（ lattice ）构造的固体。所谓格子构造，是指内部质点（原子、离子或分子）作规律排列，并构成一定的几何图形。晶体的基本要素是对称性。晶体的理想外形和晶体内部结构都具有特定的对称性。晶体的重要特征是其外部表现为规则几何外形。理想环境中生长的晶体应为凸多边形。

有些看起来像晶体的物质如玻璃、琥珀、等，它们内部质点的排列，不具有格子构造，即不作周期性的重复排列，这类固体被称之为非晶质或非晶质体。

晶体跟晶体也不同。晶体可以按照来源和成键特点分类。晶体按来源分为：天然晶体（宝石、冰、砂子等）和人工晶体（各种人工晶体材料等）。晶体按成键特点分为：原子晶体，如金刚石；离子晶体，如NaCl；分子晶体，如冰；金属晶体，如Cu。

天然晶体（natural crystal），或称天然晶体矿物，是天然产出的，具有一定化学组成和晶体结构的单质或化合物。人工晶体（synthetic crystal）即人工合成或人造的晶体。

合成晶体是有天然对应物的人工晶体。相反，人造晶体无天然对应物的人工晶体，比如人造钛酸锶，铱铝榴石（YAG），钆镓榴石（GGG）等。

人们常见的晶体有水晶、石盐、蔗糖等，在一般人的心目中就认为晶体就像水晶和石盐那样，具有规则的几何多面体形状。

晶体半导体、非晶体半导体，包括多晶体半导体都有用处。比如，硅太阳能电池就有单晶硅太能电池、非晶硅太能电池、多晶硅太能电池等等。

(2)晶体与宝石

晶体规则的几何外形和晶莹透明的漂亮颜色让人一下子想到宝石。

按晶系分类的常见宝石有：

高级晶族，如具有等轴对称性的金刚石、石榴石、尖晶石等；

中级晶族，如具有六方等轴对称性的祖母绿、海蓝宝石等；具有三方对称性的红宝石、蓝宝石、碧玺、水晶等；具有四方对称性的锆石等；

低级晶族，如具有斜方对称性的黄玉、橄榄石、金绿宝石等；具有单斜对称性的软玉、硬玉、透辉石等；具有三斜对称性的拉长石、月光石等。

这里要注意宝石与玉石的区别。宝石，如金刚石、红宝石、蓝宝石，是单晶体，即由单个矿物组成的晶体。而玉石，如翡翠、软玉、岫玉，是多晶体集合体，即由一种或多种矿物组成的集合体。

(3)半导体与宝石

“钻石恒久远一颗永流传”（A diamond is forever）是珠宝大王戴比尔斯在1939年所用的广告词。

这里的钻石即金刚石，或者说是金刚石结构的碳（C）。钻石是目前已知最硬的宝石。

纯净的钻石无色，蓝色钻石是在金刚石中掺入了少量的硼（B），而紫色钻石是在金刚石中掺入了少量的氮（N）、硼（B）、氢（H）原子。

这么珍贵的东西如果能人工制造，该是多么大的财富诱惑！事实上，很早很早以前，人们就开始了人造钻石的尝试。

1893年法国科学家莫瓦桑(Henri Moissan 1852一1907)向世人宣布他已成功地用石墨制成了世界上第一颗人造金刚石。但是, 当一些人怀疑或无法重现而向他提问时，他却以保密和专利为由谢绝。其实，他当年并没有真正从石墨中制造出金刚石，但是也没有弄虚作假。据说, 莫瓦桑坚信常压下可以制成金刚石并让助手反复试验。后来助手实在厌烦了,就事先在炉子里放了一颗金刚石。莫瓦桑不知情,还以为真的试验成功了。直到1955年，人造金刚石才由美国通用公司研制成功。

除了钻石，半导体工业中还经常用到蓝宝石、红宝石（红色和蓝色的刚玉）作为衬底。蓝宝石、红宝石的主要成分是氧化铝(Al2O3）。

纯净的氧化铝无色，蓝宝石、红宝石的颜色是其中掺入的金属使然，比如蓝宝石：氧化铝+铁（Fe）、钛（Ti）；红宝石：氧化铝+铬(Cr)。当然，蓝宝石、红宝石现在都可以人工合成，用作衬底时斑斓的色彩已无必要，所以金属掺杂就免了。

In addition to improvements in chip performance, the shell packaging technology is also a great breakthrough, IR inversion in the development of field-effect transistor, also known as "FlipFET" on the basis of this year introduced the DirectFET, as shown in Figure 6. Its source and gate inversion result can be directly welded in the printed circuit board, the drain at the top of the weld metal in its shell, if necessary, by the radiator or direct contact with the equipment enclosure. DirectFET size equivalent to the traditional SO-8 plastic (plastic with an area of about 4x5 mm2) shell. In such a small device, the first structure of a double-sided cooling. It is a lead frame, no-lead solder joints of the device, it brought about a series of advantages: it's non-resistor chip package (DFPR) is only 0. 1mW, device thickness of only 0. 7mm, resistance and parasitic inductance have dropped significantly. Such characteristics make it especially suitable for the above-mentioned computer of the latest generation of CPU. In the multi-phase circuits, each with only two of 30 security DirectFET can transfer current. Increase its current rate of 400 per delicate security, the working frequency of 1-2 MHz.

Secondly, you must be focused on power semiconductor devices in the IC direction: as a result of the development of MOSFET and IGBT, and their matching to provide a trigger signal power integrated circuit PIC (Power IC) have also developed rapidly. At that time, also known as MOS gate drive MGD (MOS Gate Driver) or control integrated circuit CIC (Control IC). With the expansion of the scope of application: such as motor drives, lighting, various power supply and so on, CIC of the cultivars have been rapidly increasing. These CIC in the development process

And gradually from a simple function to trigger the special needs of a wide range of applications development. PIC is the earliest that can be used in high voltage IC, therefore, also known as high-voltage IC (HVIC). However, many applications such as communications, computers, portable power supply and so on, they do not require high voltage, but demand for the special needs of the development of application specific integrated circuit. Because of their combination and application of power semiconductor devices, we have the power to include them in a class of semiconductor devices. So now the power semiconductor devices in the family, there are many integrated circuits. Many of these power devices with integrated circuits inside, some outside while the separation of power devices. Judging from this point, the limits of power and microelectronics has become increasingly blurred. If a large number of computer applications in power modulation device voltage LDO (Low Drop Out) is one example. It does not belong to switch applications.

As a result of a large number of integrated circuits into the power semiconductor devices, which consider the power semiconductor integrated circuits and devices to do the same in the chip or device on the development of the natural line of thought. Done in the same chip, the original is the concept of power integrated circuits, but their power often relatively small. Done in the same package, easy to increase power capacity, a number of passive components is also possible to join, here often called multi-chip module (MCM).

IR last year iPOWIR developed is a typical multi-chip module. It will power devices to control the use of integrated circuits, or in combination with pulse-width modulation (PWM) integrated circuit, according to the needs of power supply design, using BGA packaging technology portfolio in the same device (as shown in Figure 7) . Multi-chip device that greatly simplifies the power supply design staff. Components reduces the number and percentage of the area, there has been a lot of performance improvement. iPOWIR development is considered DC-DC conversion of the future. But, in fact, a wide range of applications in other fields, as long as the requirements of further integration, MCM structure and will there will be more and more. Therefore, it is the power semiconductor devices important direction of development.

In the above presentation, the development of MOSFET has been referred to as 4C industry provides an important foundation. 4C industries which, at present it is the most active direction of the product. We can understand: in the communications, computer, consumer electronics and automotive development, will require many, many close contacts and IC of all types of power semiconductor devices. Each of these aspects can be used to introduce a lot of space. Not detailed here.

Add: Conclusion

To sum up, the power semiconductor devices the past few years, constantly changed a lot. So can no longer look at a fixed vision of the development of power semiconductor devices. For example, not simply thyristor power semiconductor devices and an equal sign painting, or drawing an equal sign and discrete devices. Must not power semiconductor devices and microelectronics artificially separated, it seems only semiconductor microelectronics. These will impede the development of power semiconductor devices, in the long run will hinder the development of microelectronic devices. Development strategy in order to avoid the power semiconductor devices as a simple process only to be completed on the low-tech products. And the preferential policies available only to integrated circuit industry. China has not been very good to the development of modern power semiconductor devices, the lack of modern power semiconductor devices is a comprehensive understanding of the factors I am afraid. Information technology to stimulate industrialization in the wave, it is imperative that different semiconductor devices have a balanced development.

Conclusion

To sum up, the power semiconductor devices the past few years, constantly changed a lot. So can no longer look at a fixed vision of the development of power semiconductor devices. For example, not simply thyristor power semiconductor devices and an equal sign painting, or drawing an equal sign and discrete devices. Must not power semiconductor devices and microelectronics artificially separated, it seems only semiconductor microelectronics. These will impede the development of power semiconductor devices, in the long run will hinder the development of microelectronic devices. Development strategy in order to avoid the power semiconductor devices as a simple process only to be completed on the low-tech products. And the preferential policies available only to integrated circuit industry. China has not been very good to the development of modern power semiconductor devices, the lack of modern power semiconductor devices is a comprehensive understanding of the factors I am afraid. Information technology to stimulate industrialization in the wave, it is imperative that different semiconductor devices have a balanced development.

我自己翻译的 可以去我blog看看http://hi.baidu.com/xfsuper/blog/item/0716c43959b10ef43b87ce1a.html

化学元素Chamical Elements

化学元素

The alkali metals, found in group 1 of the periodic table (formerly known as group IA), are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements. As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The alkali metals are softer than most other metals. Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water.

碱金属被发现在元素周期表的ⅠA族，是非常活泼的金属而不在直接自然界中出现。这些金属的原子最外电子层只有1个电子。因此非常容易失去电子而与其他元素构成的离子化合物。像所有金属一样，他们具有很好的延展性并且是电和热的良导体。他们比大多数金属柔软。Cs和Fr是他们中最活泼的。碱金属接触水会爆炸。

The Alkali Metals are:

Lithium Sodium Potassium Rubidium Cesium Francium

碱金属包括：Li，Na，K，Rb，Cs，Fr

The alkaline earth elements are metallic elements found in the second group of the periodic table. All alkaline earth elements have an oxidation number of +2, making them very reactive. Because of their reactivity, the alkaline metals are not found free in nature.

碱土金属是ⅡA族中的金属元素。所有的碱土金属元素的化合价都是+2，这使他们非常活泼，因为他们非常活泼，也不在自然界中直接出现。

The Alkaline Earth Metals are:

Beryllium Magnesium Calcium Strontium Barium Radium

碱土金属金属包括Be，Mg，Ca，Sr，Ba，Ra

The 38 elements in groups 3 through 12 of the periodic table are called "transition metals". As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat. The interesting thing about transition metals is that their valence electrons, or the electrons they use to combine with other elements, are present in more than one shell. This is the reason why they often exhibit several common oxidation states. There are three noteworthy elements in the transition metals family. These elements are iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field.

元素周期表中ⅢB族到ⅡB族的38个元素叫做过渡金属。像所有金属一样，这些金属既有好的延展性也易锻造，并且是电和热的良导体。有趣之处是他们参加反应的电子层超过1层，这也是他们化合价不确定的原因（这句话不懂）。引人注目的是Fe，Co和Ni，他们是已知仅有的能产生磁场的物质的组成元素。

The Transition Metals are:

Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Ununnilium Unununium Ununbium

过渡金属包括：Sc,Y,Ti,Zr,Hf,Rf,V,Nb,Ta,Db,Cr,Mo,W,Sg,Mn,Tc,Re,Bh,Fe,Ru,Os,Hs,Co,Rh,Ir,Mt,Ni,Pd,Pt,Uun,Cu,Ag,Au,Uuu,Zn,Cd,Hg,Unb

The 7 elements classified as "other metals" are located in groups 13, 14, and 15. While these elements are ductile and malleable, they are not the same as the transition elements. These elements, unlike the transition elements, do not exhibit variable oxidation states, and their valence electrons are only present in their outer shell. All of these elements are solid, have a relatively high density, and are opaque. They have oxidation numbers of +3, ±4, and -3.

这七个被分为“其他金属”的元素位于ⅢA——ⅤA族。他们同样具有很好的延展性和段造性，但是和过渡金属不同。这些元素，不像过渡金属那样显示出可变的化合价，他们只有最外层电子参加反应。所有这七个元素都是固体，而且密度很大，并且不透明。他们的化合价一般是±3，±4。

The "Other Metals" are:

Aluminum Gallium Indium Tin Thallium Lead Bismuth

其他金属包括Al，Ga，In，Tl，Pb，Sn，Bi

Metalloids are the elements found along the stair-step line that distinguishes metals from non-metals. This line is drawn from between Boron and Aluminum to the border between Polonium and Astatine. The only exception to this is Aluminum, which is classified under "Other Metals". Metalloids have properties of both metals and non-metals. Some of the metalloids, such as silicon and germanium, are semi-conductors. This means that they can carry an electrical charge under special conditions. This property makes metalloids useful in computers and calculators

半金属是金属和非金属之间的过渡区。这条线从B，Al一直画到Po和At。之中唯一的特例是Al，它属于其他金属。半金属兼有金属和非金属的特性。例如Si和Ge，他们是半导体，也就是说他们在特殊情况下他们可以导电。这种特性使半金属在计算器和电脑领域很有用。

The Metalloids are:

Boron Silicon Germanium Arsenic Antimony Tellurium Polonium

半金属包括B，SI，Ge，As，Sb，Te，Po

Non-metals are the elements in groups 14-16 of the periodic table. Non-metals are not able to conduct electricity or heat very well. As opposed to metals, non-metallic elements are very brittle, and cannot be rolled into wires or pounded into sheets. The non-metals exist in two of the three states of matter at room temperature: gases (such as oxygen) and solids (such as carbon). The non-metals have no metallic luster, and do not reflect light. They have oxidation numbers of ±4, -3, and -2.

非金属是是元素周期表中ⅣA-ⅥA族的元素。非金属不能很好的导电或导热，与金属元素相反，他们不能被锻造成丝或箔，反而非常易碎。非金属元素在室温下为固态或液态。非金属没有金属一样的光泽，也不反光，他们的化合价为±4, -3, 和 -2.

The Non-Metal elements are:

Hydrogen Carbon Nitrogen Oxygen Phosphorus Sulfur Selenium

非金属元素包括H，C，N，O，P，S，Se

The halogens are five non-metallic elements found in group 17 of the periodic table. The term "halogen" means "salt-former" and compounds containing halogens are called "salts". All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. The halogens exist, at room temperature, in all three states of matter:

Solid- Iodine, Astatine Liquid- Bromine Gas- Fluorine, Chlorine

卤素是ⅦA族中的5钟非金属元素，卤素的意思来源于希腊语halos（盐）和gennan（形成）两个词。在中文里，卤的原意是盐碱地的意思。所有的卤族元素的原子最外层都有7个电子。这使他们显现-1价。在室温下卤族元素构成的物质可表现为任何状态。

The Halogens are:

Fluorine Chlorine Bromine Iodine Astatine

卤族元素包括F，Cl，Br，I，At

The six noble gases are found in group 18 of the periodic table. These elements were considered to be inert gases until the 1960's, because their oxidation number of 0 prevents the noble gases from forming compounds readily. All noble gases have the maximum number of electrons possible in their outer shell (2 for Helium, 8 for all others), making them stable.

6种稀有气体是元素周期表0族的元素。在20世纪60年代以前，他们被认为是惰性气体，因为他们0的化合价让他们不与其他元素反应。所有稀有气体的最外电子层都满了。（He是2，其他是8个电子），使它们稳定。

Helium Neon Argon Krypton Xenon Radon

稀有气体包括He，Ne，Ar，Kr，Xe，Rn

The thirty rare earth elements are composed of the lanthanide and actinide series. One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made. All of the rare earth metals are found in group 3 of the periodic table, and the 6th and 7th periods. The Rare Earth Elements are made up of two series of elements, the Lanthanide and Actinide Series.

三十个稀土金属是稳定的La系和Ac系元素。La系中的一个和Ac系中的大多数被人们叫做反铀元素，或者是人造的。所有稀土元素都位于第三族，第六和第七族，被分为La系和Ac系（……）。

The Rare Earth Elements are:

Lanthanide Series

Actinide Series

Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium

Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium

稀土金属包括La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Ac,Th,Pa,U,Np,Pu,Am,Cm,Bk,Cf,Es,Fm,Md,No,Lr

这一篇还可以

英国化学家戴维，1778年出生于彭赞斯。因他父亲过早去世。母亲无法养活五个孩子，于是卖掉田产，开起女帽制作店来。但他们的日子还是越过越苦。 戴维从小就勇于探索，他的兴趣很广泛。他在学校最喜欢的是化学，常常自己做实验。

17岁的时候，戴维到博莱斯先生的药房当了学徒。既学医学，也学化学，除读书外，他还做些较难的化学实验，为此，人们送他一个“小化学家”的称号。

一天，一个叫贝多斯的物理学家，登门拜访了这位“小化学家”，并邀请他到条件很好的气体研究所去工作。

戴维欣然受聘，来到贝多斯的研究所。该所想通过研究各种气体对人体的作用，弄清哪些气体对人有益，哪些气体对人有害。

戴维接受的第一项任务是配制氧化亚氮气体。戴维不负重望，很炔就制出这种气体。当时，有人说这种气体对人有害，而有的人又说无害，各持己见，莫衷一是。制得的大量气体，只好装在玻璃瓶中留着备用。

1799年4月的一天，贝多斯来到戴维的实验室，见已制出许多氧化亚氮，高兴地说：“啊，不错，您的工作令人十分满意……”贝多斯夸奖戴维的话还未说完，他一转身，不小心手把一个玻璃瓶子碰到地下打碎了。

戴维慌忙过来一看，打碎的正是装氧化亚氮的瓶子，忙问：“手不要紧吧？”

“没事。真对不起，我把您的劳动成果浪费了。”贝多斯边说边拣碎玻璃。

“没啥，我正要作试验呢，想看看这种气体对人究竟会有什么影响，这样一来还省得我开瓶塞……”戴维的话还未说完，被贝多斯反常的表情弄得惊慌失措。

“哈哈哈……”一向沉着、孤僻、严肃得几乎整天板着面孔的贝多斯，今天突然大笑起来，“戴维，哈哈哈……我的手一点儿都不疼，哈哈哈……”“哈哈哈……”刚才还处于惊慌的戴维也骤然大笑，“真的不疼？哈哈哈……”

两位科学家的笑声，惊动了隔壁实验室的人。他们跑来一看，都以为他俩得了神经病。等一阵狂笑之后，两人方逐渐清醒。贝多斯被玻璃划破的手指感到疼痛，原来氧化亚氮不仅使他俩狂笑，而且使贝多斯麻醉不知手痛。

事隔不久，戴维患了牙病，便请来牙科医生德恩梯斯·舍派特。医生决定把他的坏牙拔掉。当时根本没有什么麻醉药，医生硬把牙齿给拉了下来，疼得戴维浑身冒汗。这时，他猛然想起前不久发生的事——贝多斯手划破了，可闻了那氧化亚氮后却一点也没感觉疼。于是，他赶忙拿过装有氧化亚氮的瓶子连吸几口，结果，他又哈哈大笑起来，同时也感觉不到牙痛了。

经过进一步研究，戴维证实氧化亚氮不仅能使人狂笑，而且还有一定的麻醉作用。戴维就为这种气取了个形象的名字笑气。

戴维将关于笑气的研究成果写进《化学和哲学研究》一书，立即轰动了整个欧洲。外科医生们纷纷用笑气做麻醉药，使本来满是刺耳的喊叫声的手术室，弥漫着一片笑声。病人的痛苦也轻多了。

戴维发现笑气的时候，年仅21岁。从此，他成了闻名欧洲的青年科学家。

后来，戴维继续从事科学研究，首先制取了金属钾、钠、钙、镁、钡和非金属硼，还发明了矿工用的安全灯。为人类做出了很大的贡献。

British chemist David, was born in 1778 in Penzance. As a result of his father's premature death. Not the mother of five children to feed, then sell the farm, started millinery shop to produce. But their day is over the more bitter. David from an early age have the courage to explore his interest in a wide range. His favorite is the school of chemical, often their own experiments.

17-year-old, Mr. David to the BLS as a pharmacy apprentice. Both the medical school, school chemistry, in addition to reading, he's also more difficult to do chemical experiments, for which he was sent to a "chemist".

One day, a man named Tony Meadows physicist, had to visit the "chemist" and invited him to the very good conditions for the gas to the work of the Institute.

However, Dai Weixin employed, Tony came to the meadows of the Institute. The study through a variety of gases on the human body, out of gas which were beneficial and which harmful gases.

David to accept the first task is the preparation of nitrous oxide gas. David does not live up, it is such a system on acetylene gas. At that time, it is said that this harmful gas, and some people said that sound, to hold different views, rather than consensus. Obtained a large number of gas, had no choice but to keep in glass bottles mounted on a stand-by.

In April 1799 of the day, Tony came to David Doss of the laboratory, see the system has a lot of nitrous oxide, said happily: "ah, yes, your work is very pleased with the ... ..." Tony praised David Doss The words have not yet finished, he turned a careless hand on the ground floor of a glass bottle smashed across sub.

David hurriedly looked around, broke the bottle of nitrous oxide is loaded, Mangwen: "It does not matter in hand?"

"Never. I'm sorry, I am your labor lost." Meadows said, picking shellfish broken glass.

"Nothing, I am going to trial, would like to see this person on the gas What does it mean, this way also to save me ... ... cork" David's words have not yet finished, Tony Adams and more abnormal Look up panic.

"Ha, ha, ha ... ..." always been cool, eccentric, a serious Banzhuomiankong almost the whole day of the Tony Meadows, all of a sudden today, laughing, "David, Ha, ha, ha ... ... My hands are a little pain, ... Ha, ha, ha ... "" Ha, ha, ha ... ... "in a panic just yet David is also a sudden laugh," really hurt? ... Ha, ha, ha ... "

The two scientists laughter, alerted the laboratory next door. They came to see one, they all thought had neuropathy. Kuang Xiao, and so on for a while, the two sides gradually clear. Tony Adams has been more than cut through the glass finger pain that Kuang Xiao nitrous oxide not only they but also the multi-Tony Adams hand I do not know of narcotic pain.

Soon after, David is suffering from dental problems, we have invited dentists Dehn Ossetia Pat Adams homes. Doctors decided his bad tooth pulled out. At that time, there was not any anesthetic, the doctor forcibly teeth to pull down, David painful sweating all over. At this time, he suddenly reminded of what happened long ago - more than Tony Adams cut through the hand, can be heard and that the nitrous oxide after it did not feel a little pain. As a result, he quickly took the bottle of nitrous oxide with even a few smoke as a result, he laughed, at the same time feel a toothache.

After further study, confirmed that David nitrous oxide Kuangxiao not only make the people, but also a certain narcotic effect. David was on the air that took the name of the image of a laughing gas.

David will be laughing gas on the results of research into the "chemical and philosophical studies", the immediate sensation throughout Europe. Surgeons who have used nitrous oxide anesthesia to do so have been full of ear-piercing cries of the operating room, filled with a laugh. Patients are suffering more than the light.

David found that nitrous oxide, as young as 21 years old. Since then, he has become famous for Europe's young scientists.

Later, David continued to engage in scientific research, first of all, making the metal potassium, sodium, calcium, magnesium, boron and non-metallic barium, also invented the miner's safety lamp used. Mankind has made a great contribution.

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