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Femtosecond Laser-Induced Crystallization of Amorphous Silicon Thin Films under a Thin Molybdenum Layer
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-07-28 , DOI: 10.1021/acsami.1c07083 Nazar Farid 1 , Adam Brunton 2 , Phil Rumsby 2 , Scott Monaghan 3, 4 , Ray Duffy 3 , Paul Hurley 3, 4 , Mingqing Wang 5 , Kwang-Leong Choy 5 , Gerard M O'Connor 1
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-07-28 , DOI: 10.1021/acsami.1c07083 Nazar Farid 1 , Adam Brunton 2 , Phil Rumsby 2 , Scott Monaghan 3, 4 , Ray Duffy 3 , Paul Hurley 3, 4 , Mingqing Wang 5 , Kwang-Leong Choy 5 , Gerard M O'Connor 1
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A new process to crystallize amorphous silicon without melting and the generation of excessive heating of nearby components is presented. We propose the addition of a molybdenum layer to improve the quality of the laser-induced crystallization over that achieved by direct irradiation of silicon alone. The advantages are that it allows the control of crystallite size by varying the applied fluence of a near-infrared femtosecond laser. It offers two fluence regimes for nanocrystallization and polycrystallization with small and large crystallite sizes, respectively. The high repetition rate of the compact femtosecond laser source enables high-quality crystallization over large areas. In this proposed method, a multilayer structure is irradiated with a single femtosecond laser pulse. The multilayer structure includes a substrate, a target amorphous Si layer coated with an additional molybdenum thin film. The Si layer is crystallized by irradiating the Mo layer at different fluence regimes. The transfer of energy from the irradiated Mo layer to the Si film causes the crystallization of amorphous Si at low temperatures (∼700 K). Numerical simulations were carried out to estimate the electron and lattice temperatures for different fluence regimes using a two-temperature model. The roles of direct phonon transport and inelastic electron scattering at the Mo–Si interface were considered in the transfer of energy from the Mo to the Si film. The simulations confirm the experimental evidence that amorphous Si was crystallized in an all-solid-state process at temperatures lower than the melting point of Si, which is consistent with the results from transmission electron microscopy (TEM) and Raman. The formation of crystallized Si with controlled crystallite size after laser treatment can lead to longer mean free paths for carriers and increased electrical conductivity.
中文翻译：
薄钼层下非晶硅薄膜的飞秒激光诱导结晶
提出了一种结晶非晶硅的新工艺，该工艺不会熔化，也不会对附近的部件产生过度加热。我们建议添加钼层，以提高激光诱导结晶的质量，优于仅直接照射硅所实现的结晶质量。优点是它可以通过改变近红外飞秒激光的应用通量来控制微晶尺寸。它为纳米晶化和多晶化提供两种注量范围，分别具有小晶粒尺寸和大晶粒尺寸。紧凑型飞秒激光源的高重复率可实现大面积的高质量结晶。在该方法中，用单个飞秒激光脉冲照射多层结构。该多层结构包括衬底、涂覆有附加钼薄膜的目标非晶硅层。通过在不同注量范围下照射Mo层来使Si层结晶。能量从受辐射的 Mo 层到 Si 膜的转移导致非晶硅在低温（~700 K）下结晶。使用双温度模型进行数值模拟，以估计不同注量范围的电子和晶格温度。 Mo-Si 界面上的直接声子输运和非弹性电子散射在能量从 Mo 到 Si 薄膜的转移中的作用被考虑。模拟证实了非晶硅在低于硅熔点的温度下以全固态过程结晶的实验证据，这与透射电子显微镜（TEM）和拉曼的结果一致。 激光处理后形成具有受控微晶尺寸的结晶硅可以导致载流子平均自由程更长并提高电导率。
更新日期：2021-08-11
中文翻译：
薄钼层下非晶硅薄膜的飞秒激光诱导结晶
提出了一种结晶非晶硅的新工艺，该工艺不会熔化，也不会对附近的部件产生过度加热。我们建议添加钼层，以提高激光诱导结晶的质量，优于仅直接照射硅所实现的结晶质量。优点是它可以通过改变近红外飞秒激光的应用通量来控制微晶尺寸。它为纳米晶化和多晶化提供两种注量范围，分别具有小晶粒尺寸和大晶粒尺寸。紧凑型飞秒激光源的高重复率可实现大面积的高质量结晶。在该方法中，用单个飞秒激光脉冲照射多层结构。该多层结构包括衬底、涂覆有附加钼薄膜的目标非晶硅层。通过在不同注量范围下照射Mo层来使Si层结晶。能量从受辐射的 Mo 层到 Si 膜的转移导致非晶硅在低温（~700 K）下结晶。使用双温度模型进行数值模拟，以估计不同注量范围的电子和晶格温度。 Mo-Si 界面上的直接声子输运和非弹性电子散射在能量从 Mo 到 Si 薄膜的转移中的作用被考虑。模拟证实了非晶硅在低于硅熔点的温度下以全固态过程结晶的实验证据，这与透射电子显微镜（TEM）和拉曼的结果一致。 激光处理后形成具有受控微晶尺寸的结晶硅可以导致载流子平均自由程更长并提高电导率。
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