Internal Photoemission Metrology of Inhomogeneous Interface Barriers

Abstract

Interfaces of heterogeneous solids, ranging from polycrystalline materials to composites, are frequently encountered in nanotechnology. Electron transport in these materials and across their interfaces critically depends on the energy barriers electrons encounter on their way. Because of electrode structural heterogeneity, the barriers may exhibit significant spatial variations resulting in a broad distribution of barrier heights and built-in potentials. Quantification of the distributed interface barriers represents a formidable experimental challenge since direct association of interface properties with those of an outer free surface is generally inaccurate. Here we present a methodology enabling quantification of electron barriers at interfaces of semiconductors and metals with insulators using the electric field-dependent internal photoemission (IPE) of electrons. It is shown that practically relevant interfaces may contain "patches" with differences in barrier height (or the effective work function) of up to 1 eV, which makes the electrode heterogeneity a crucial factor in designing electron devices suitable for low-voltage operation.

Mechanisms of Oxygen Vacancy Aggregation in SiO2 and HfO2

“…The charge transition levels of these vacancies exhibit a similar spread with an average 0/-1 charge transition level of 6.9 eV and an average -1/-2 charge transition level of 7.0 eV. Our results indicate that the charge transition levels which correspond to negatively charged vacancies are well positioned in relation to the conduction band of Si [46] and Fermi level position of some metal electrodes [47]. Thus, the newly created O vacancies can support trap assisted electron tunneling through a-SiO 2 in Si/SiO 2 /metal stacks.…”

Assessment of Energy Barriers Between ZrCuAlNi Amorphous Metal and Atomic Layer Deposition Insulators Using Internal Photoemission Spectroscopy

“…X‐ray photoelectron spectroscopy (XPS) is limited to the material properties in vacuum, rather than in intimate contact with another material with which there may be interactions. Internal photoemission (IPE) spectroscopy, on the other hand, is a well‐established electro‐optical technique that allows direct measurement of specific interfacial energy barriers within a device structure . Although IPE has been widely used to characterize the interfaces between various polycrystalline elemental metals and oxides within MOS structures, there have only been a few reports of IPE within MIM structures, many of which were on native oxides rather than high quality deposited oxides, and no reports of IPE on amorphous electrodes.…”

“…The portion of the Y 1/2 ( hν ) plot used for determination of φ thresh , referred to as the extraction window, can significantly affect the final extracted barrier height ( φ Bn ). Considerations for the extraction window include photoconduction at high photon energies, sub‐threshold emission at lower energies either into band‐tail states of the conduction band or defect levels in the oxide, and lateral non‐uniformity of the barrier . In this work, φ thresh extraction was performed using an algorithm which employed a moving window to determine the region of highest linearity from the yield curves by comparing the coefficient of determination for each window.…”

Inhibition of Oxygen Scavenging by TiN at the TiN/SiO2 Interface by Atomic-Layer-Deposited Al2O3 Protective Interlayer

“…In fact, using the same material, for example, TiN, one can modulate its effective WF (EWF) in a sufficiently wide range by using ion implantation, Al doping, SiH 4 soak, etc. There is a potential to attain a nearly 1 eV EWF modulation range using TiN as the electrode material as suggested to the comparison of the Fermi level positions between TiN layers deposited on SiO 2 using different physical vapor deposition (PVD) techniques, compare Figure 7 in ref . The critical element in “setting” the EWF value appears to be the modulation of the nitrogen content in the metallic TiN.…”