Room-Temperature Quantum Transport Phenomenon in Low-Temperature-Grown Zn_1–xMg_xO/ZnO Heterostructures

Abstract

Quantum transport phenomenon such as quantum Hall effect usually appears up at cryogenic temperature. Here, we observe a room-temperature quantum transport phenomenon in ZnO-based two-dimensional systems. We successfully fabricate Zn1–x Mg x O/ZnO heterostructures by using magnetron sputtering with a low growth temperature which makes it feasible to obtain flexible heterostructures. Electrical transport properties of these heterostructures are studied. A parabolic negative magnetoresistance is clearly observed in a wide temperature range, which can be accurately described by the weak localization theory. By analyzing the temperature dependence of the dephasing length, it is found that the electron–electron scattering combined with two-dimensional electron–phonon scattering dominates the dephasing process for electrons. Importantly, the observed negative magnetoresistance persists up to 300 K. This indicates that room-temperature weak localization effect appears up, which can be attributed to weak electron–phonon scattering and small electron mobility. The present work provides a reference for realizing room-temperature quantum effect which is beneficial to develop quantum-interference devices.

Low-temperature positive magnetoresistance in ZnO-based heterostructures

“…The same situation also appears up in polycrystalline Zn 1−x Mg x O/ZnO heterostructures [14,15]. In our samples, 2DEG has been proved to be formed (see a sketch in figure 1(a)) [11]. The n H values (see table 1) are comparable to the reported results in polycrystalline Zn 1−x Mg x O/ZnO heterostructures [14,15].…”

“…This point is understandable because the mean free path l (1 ∼ 4 nm) is smaller than the grain size (8 ∼ 15 nm) of transport channel (i.e. ZnO layer) [11]. Meanwhile, we find that µ H exhibits a linear dependence on T 3/2 for all our samples (see figure 1(d)), which indicates that the ionized impurity scattering dominantly limits µ H [18].…”

“…The sheet resistance (R sh ) for all our four samples are far less than 25 kΩ over the whole studied T range of 2-300 K [11]. According to the expression k F l ≈ 25 kΩ/R sh (k F is the Fermi wave vector), the value for k F l is found to vary between 3 and 76 for all our samples (i.e.…”

“…The grown samples had been characterized by xray diffraction, atomic force microscopy, and scanning electron microscopy. The measured data can be seen in our previous work [11].The Hall-bar-shaped samples were defined by using a mask for the transport measurement. The metallic aluminum was used to form Ohmic contacts.…”

Self-Complementary Dimer of Zinc(II) Porphyrins through Coordination with Oxygen Ligands

“…For example, Kobuke has reported the synthesis of N -methylimidazole–Zn-porphyrin dimer in a slipped cofacial orientation 43 as well as macrocyclic porphyrin arrays by complementary coordination of m -bis(ethynylene)phenylene-linked imidazolylporphyrin. 37 Oxygen ligands, such as carbonyl, 44 45 hydroxyl, 46 47 48 ether, 45 , 49 50 51 sulfoxide, 52 and phosphine oxide 53 54 55 groups, have also been shown to play an critical role in the formation and organization of metalloporphyrin assemblies and natural chlorosomes. In line with our recent interests in polynorbornenes appended with N -arylpyrrolidine and related polymers, we have synthesized several kinds of norbornene and 7-oxanorbornene intermediates such as 1a and 1b (Scheme 1 ) for the preparation of the desired polymers.…”