Semiconductor Spintronics and Molecular Electronics Micro-and Nanodevices for Detection of Biologically Relevant Molecules

  • Tamador Alkhidir

Student thesis: Doctoral Thesis


Semiconductor-spintronics is a fast-growing field which this work contributes to in terms of the chemical properties of bio-relevant substances. The operation of semiconductor-spintronics relies on manipulating both the spin and the charge of electrons adding an extra degree of freedom in biosubstance detection. In this dissertation, we have developed gallium arsenide (GaAs) spintronic device promoting both chemical and nuclear magnetic sensing applications. In terms of magnetic sensing, we report the first demonstration of optically detected nuclear magnetic resonance (NMR) of 1H in water surrounding GaAs spin-light emitting (LED) diode. The ferromagnetic layer in GaAs spin-LED structure assures high injection of electrically polarized electrons into GaAs. The NMR optical detection is accessible due to the sensitivity of the excited electron spins to the local polarized nuclei (75As,69Ga,71Ga,1H). We demonstrate that as few as 105 - 106 1H spins could be detected in the optically measured NMR. This observation indicates higher sensitivity in comparison to the conventional NMR setup that required at least several orders of magnitude more spins for acceptable NMR signal. The strength of the NMR signal was studied in different values of temperature, applied magnetic field and electric field (device voltage bias). This study should pave the way for the future development of fully handheld close to room temperature devices. The sensitivity of the GaAs surface makes it a good candidate for sensing various molecular species of interest in biochemistry. Simultaneously, the growth in nanofluidics applications calls for detailed understanding of liquid-solid interfaces for a variety of interfaces combinations. The approximately 1 V operation range for GaAs spin-LED is shown to be sufficient to detect OH−, OD−, as well as PBS solutions of various concentrations at 300K. Inorganic bonds, such as Ga-H, Ga-O (and related As-based ones), are differentiated through correlation of transport and FTIR data of liquid-solid interfaces. The same GaAs diode-like sensor could be used to distinguish between different types of amino acids (non-polar, polar, and basic) through the specific examples of glycine, L-histidine, and L-cystine, respectively. Finally, the conductance is determined as a function of the pH factor of solutions tested (4
Date of AwardDec 2019
Original languageAmerican English


  • Spintronics
  • Molecular Electronics
  • NMR
  • DNP
  • Semiconductor
  • Amino Acids
  • Bio-sensors

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