Ultrafast terahertz dynamics of materials

材料的超快太赫兹动力学

• 批准号: RGPIN-2016-05842
• 负责人: Hegmann, Frank
• 金额: $ 3.64万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633242
• 关键词: Ultrafast; terahertz; dynamics; materials

Many fundamental processes in nature occur over ultrafast time scales measured in picoseconds, or trillionths of a second. For example, in semiconductor materials like those used in computer chips and digital cameras, electrons can move freely in one direction for about a tenth of a picosecond before getting bumped in a different direction by small vibrations of the atoms. This scattering of electrons over such short time scales affects the flow of electrical current in materials. A pure semiconductor can actually be a good insulator, but absorption of light can generate both negative (electron) and positive (“hole”) charge carriers that are then free to move, making the material conducting. This phenomenon, which is called photoconductivity, forms the basis of most light sensing technologies. The photoexcited electrons and holes can move around inside the material for up to a few nanoseconds before becoming trapped at defect sites or emitting light as they recombine. In semiconductor nanomaterials, the lifetimes of photoexcited charge carriers can be tens of picoseconds, depending on the nanoscale morphology of the material.

自然界中的许多基本过程发生在以皮秒或万亿分之一秒为单位的超快时间尺度上。例如，在计算机芯片和数码相机中使用的半导体材料中，电子可以在一个方向上自由运动约十分之一皮秒，然后被原子的微小振动撞向不同的方向。电子在如此短的时间尺度上的散射会影响材料中的电流流动。纯半导体实际上可以成为良好的绝缘体，但光的吸收可以产生负(电子)和正(空穴)载流子，然后这些载流子可以自由移动，使材料导电。这种现象被称为光电导性，构成了大多数光敏技术的基础。光激发的电子和空穴可以在材料内部移动长达几纳秒，然后被困在缺陷位置或在重新结合时发光。在半导体纳米材料中，光激发载流子的寿命可以是几十皮秒，这取决于材料的纳米级形貌。