Electrical and chemical characterizations of hafnium (IV) oxide films for biological lab-on-a-chip devices
Electrical and chemical characterizations of hafnium (IV) oxide films for biological lab-on-a-chip devices
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DOI：
10.1016/j.tsf.2018.07.024
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发表时间：
2018-09-30
期刊：
影响因子：
2.1
通讯作者：
Minerick, A. R.
中科院分区：
文献类型：
--
作者：
Collins, J. L.;Hernandez, H. Moncada;Minerick, A. R.
许多生物芯片实验室应用需要电学和光学操作以及细胞和生物分子的检测。这为设计坚固的微器件提供了一个有趣的挑战，既能抵抗不良的电化学副反应，又能实现光学透明度。从微电极上物理隔离生物样品可以防止污染、电极污垢和电化学副产物；因此，本文探讨了氧化铪（HfO2）薄膜-起源于传统的晶体管应用-在生物应用的电动微流体装置中的适用性。在硅基片和玻璃基片上溅射制备了沉积时间分别为6.5、13和20 min的HfO2薄膜。利用原子力显微镜（AFM）、x射线衍射、能量色散x射线能谱、傅里叶变换红外光谱、椭偏仪和电容电压对HfO2薄膜的结构、光学和电学性能进行了研究。HfO2薄膜的电势模拟和生物相容性研究提供了额外的见解。用原子力显微镜观察腐蚀水虎鱼处理后膜的晶粒大小。通过x射线衍射研究发现，所有薄膜都表现出（111）特征峰，较厚的薄膜表现出多峰，表明各向异性结构。场发射扫描电镜x射线能谱和傅里叶变换红外光谱均证实了膜的原子比为HfO2。Si的椭偏测量数据测得HfO2的厚度分别为58、127和239 nm，折射率和消光系数均在正常范围内；由于薄膜和衬底的透明度，玻璃数据产生了不可靠的厚度验证。电容-电压结果产生的平均介电常数为20.32，模拟表明HfO2的介电特性足以电钝化平面微电极。通过测定HfO2膜的溶血潜能，确定HfO2与人红细胞的生物相容性。总体结果支持氧化铪作为一种可行的钝化材料的生物实验室芯片上的应用。
Many biological lab-on-a-chip applications require electrical and optical manipulation as well as detection of cells and biomolecules. This provides an intriguing challenge to design robust microdevices that resist adverse electrochemical side reactions yet achieve optical transparency. Physical isolation of biological samples from microelectrodes can prevent contamination, electrode fouling, and electrochemical byproducts; thus this manuscript explores hafnium oxide (HfO2) films - originating from traditional transistor applications - for suitability in electrokinetic microfluidic devices for biological applications. HfO2 films with deposition times of 6.5, 13, and 20 min were sputter deposited onto silicon and glass substrates. The structural, optical, and electrical properties of the HfO2 films were investigated using atomic force microscopy (AFM), X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, ellipsometry, and capacitance voltage. Electric potential simulations of the HfO2 films and a biocompatibility study provided additional insights. Film grain size after corrosive Piranha treatment was observed via AFM. The crystalline structure investigated via X-ray diffraction revealed all films exhibited the (111) characteristic peak with thicker films exhibiting multiple peaks indicative of anisotropic structures. Energy dispersive X-ray spectroscopy via field emission scanning electron microscopy and Fourier transform infrared spectroscopy both corroborated the atomic ratio of the films as HfO2. Ellipsometry data from Si yielded thicknesses of 58, 127, and 239 nm and confirmed refractive index and extinction coefficients within the normal range for HfO2 ; glass data yielded unreliable thickness verifications due to film and substrate transparency. Capacitance-voltage results produced an average dielectric constant of 20.32, and the simulations showed that HfO2 dielectric characteristics were sufficient to electrically passivate planar microelectrodes. HfO2 biocompatibility was determined with human red blood cells by quantifying the hemolytic potential of the HfO2 films. Overall results support hafnium oxide as a viable passivation material for biological lab-on-a-chip applications.