HOPG Substrate Research Articles

X-ray Spectroscopy of a Rare-Earth Molecular System Measured at the Single Atom Limit at Room Temperature.

We investigate the limit of X-ray detection at room temperature on rare-earth molecular films using lanthanum and a pyridine-based dicarboxamide organic linker as a model system. Synchrotron X-ray scanning tunneling microscopy is used to probe the molecules with different coverages on a HOPG substrate. X-ray-induced photocurrent intensities are measured as a function of molecular coverage on the sample, allowing a correlation of the amount of La ions with the photocurrent signal strength. X-ray absorption spectroscopy shows cogent M4,5 absorption edges of the lanthanum ion originated by the transitions from the 3d3/2 and 3d5/2 to 4f orbitals. X-ray absorption spectra measured in the tunneling regime further reveal an X-ray excited tunneling current produced at the M4,5 absorption edge of the La ion down to the ultimate atomic limit at room temperature.

Direct etching of nano/microscale patterns with both few-layer graphene and high-depth graphite structures by the raster STM electric lithography in the ambient conditions.

The development of raster STM electric lithography has enabled the etching of nano/microscale patterns on both few-layer graphene (FLG) and high-depth graphite structures on the bulk HOPG substrates under ambient conditions. This approach utilises a nanoscale probe tip as a machining tool to directly fabricate conductive sample surfaces without the need for resists or masks. Compared to conventional nano/micro machining methods, the capability of ultraaccurate fabrication of nanoscale patterns using this technique is unmatched. The resulting FLG structures exhibit ultrasmooth flat bottoms and uniformly controlled depths ranging from 0.34 to 3.0nm (less than 10 layers). This work represents a significant advancement as it demonstrates the perfect etching of FLG structures in designated nano/microscale regions using raster STM electric lithography in the constant current mode, which reaches the limitation of top-down manufacturing techniques. Additionally, raster STM electric lithography in the constant height mode can directly etch high-depth structures (up to ∼100nm). The geometric shape and number of layers of the etched graphene structures determined by either local anodic oxidation (LAO) or the electric discharge (ED) mechanism. The LAO mechanism results in less debris and smoother edges compared to the ED mechanism, which is caused by the random electrical discharge between the tip and the sample. The well-controlled raster STM electric lithography technique is believed to be a promising and facile approach for constructing nano/microscale graphene-based devices.

Manipulating single excess electrons in monolayer transition metal dihalide

Polarons are entities of excess electrons dressed with local response of lattices, whose atomic-scale characterization is essential for understanding the many body physics arising from the electron-lattice entanglement, yet difficult to achieve. Here, using scanning tunneling microscopy and spectroscopy (STM/STS), we show the visualization and manipulation of single polarons in monolayer CoCl2, that are grown on HOPG substrate via molecular beam epitaxy. Two types of polarons are identified, both inducing upward local band bending, but exhibiting distinct appearances, lattice occupations and polaronic states. First principles calculations unveil origin of polarons that are stabilized by cooperative electron-electron and electron-phonon interactions. Both types of polarons can be created, moved, erased, and moreover interconverted individually by the STM tip, as driven by tip electric field and inelastic electron tunneling effect. This finding identifies the rich category of polarons in CoCl2 and their feasibility of precise control unprecedently, which can be generalized to other transition metal halides.

Comparative studies of properties of CdSe/POMA hybrid films electrodeposited on HOPG, Au and Pt substrates

A simple deposition method was used to prepare photoactive composites containing cadmium selenide (CdSe) and poly(o-methoxyaniline) (POMA) nanofilms deposited on various substrates: HOPG, Au and Pt. The films were fabricated in a configuration substrate/CdSe/POMA. The deposition conditions were electrode substrate dependent. It was determined that the lowest required energy for initiation of polymer deposition is in the order of HOPG<Au<Pt substrate. The photovoltage and photocurrent of fabricated composites depend on the substrate underneath. The highest photocurrents 1.4 mAcm–2 were observed for Pt/CdSe/POMA, while the highest photovoltage 406 mV and 455 mV was registered for Au/CdSe/POMA and Pt/CdSe composites. The AFM and XPS studies explained the influence of the deposition substrate on the formed hybrid's quality. The photodegradation mechanism of CdSe/POMA hybrid was proposed and the role of POMA layer was explained. It was detected that the recombination process depends on a structure of deposited layers. As determined by AFM, CdSe and POMA films are the most crystalline when deposited on Pt, what enhanced photocurrent comparing to other substrates. The thickness of the electrodeposited POMA films decreases in the order HOPG>Au>Pt substrates as concluded from the XPS spectra. The observed metal/CdSe/POMA electrodes restructuring may be explained as the formation of selenates, selenosulfites and hydrogen sulfide due the sacrifizing role of the polymer.

(Invited) Monolayer h-BN: Epitaxy, Properties, and Emerging Device Applications

Hexagonal boron nitride (h-BN) has shown tremendous promise when used alongside other two-dimensional (2D) materials such as graphene, and as a wide-bandgap semiconductor for deep-ultraviolet optoelectronics and quantum photonics. Owing to its large bandgap energy comparable or higher than Al(Ga)N, h-BN can be used to form heterostructures to address some of the critical challenges of Al(Ga)N-based systems. To date, however, many fundamental material properties of h-BN remain unknown. For example, its bandgap energy remains under debate, with reports spanning from 5.9 to 6.5 eV. There is also strong controversy as to whether h-BN has a direct or indirect bandgap. In this context, We have studied the epitaxy of h-BN by using ultrahigh temperature (up to 1850 °C) plasma-assisted molecular beam epitaxy (MBE) on sapphire, Ni and HOPG substrates. We show that, when grown at sufficiently high temperature, h-BN can exhibit predominantly excitonic emission at ~220 nm. The measured luminescence intensity is orders of magnitude higher than AlN under identical conditions. By forming a p-i-n structure using this high-quality h-BN as the active region, the current-voltage (I-V) and electroluminescence characteristics of a first demonstration of a h-BN deep UV LED will be reported.

Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: In Situ Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition

Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: <i>In Situ</i> Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition

KPFM and DFT as tools to correlate the charge distribution and molecular orientation of dendritic adsorbates on different surfaces

The interaction between metals and organic layers is currently a hot topic due to its relevance in future applications based on hybrid organic/inorganic systems at the nanoscale. This work studies the surface modification of HOPG and gold substrates by spontaneous adsorption of aryl-dendrons based on either 3,5-bis(3,5-dinitrobenzoylamino) or 3,5-bis(3,5-diaminobenzoylamino) benzoic acids at fully controlled conditions. KPFM is used to assess the local work function variations upon assembly. A correlation between changes in work function values and spatial ordering of the adsorbates is observed. The aryl-dendrons interact with graphite surfaces through π-π stacking, allowing the formation of ordered layers. Due to depolarization effects, these films cause changes in the local work function values that are smaller on graphite surfaces than on gold substrates. Furthermore, the presence of molecular aggregates driven by intermolecular hydrogen bonding for the case of amino functionalized surfaces has a direct impact on the local work function, which varies depending on whether the areas are partially covered or densely packed. DFT calculations were performed in order to gain a deeper understanding of the correlation between the work function variations and the orientation of the effective molecular dipole moment due to the underlying molecular structures of the adsorbed layer.

Nano-films of carbo-benzene derivatives: Scanning probe microscopy analysis and prospects of use in organic solar cells

Three carbo-mer derivatives based on a C18Ph4 core decorated with two identical electro-active groups X, i.e. two aromatic carbo-benzenes (1 and 2, X = 4-anilinyl) and one pro-aromatic carbo-quinoid (the carbo-TTF 3, X = 1,3-dithiol-2-ylidene) were studied through Scanning Probe Microscopies (SPMs). Self-Assembled Monolayers (SAMs) were fabricated (thickness ~160 pm), for the two centrosymmetric representatives 1 and 3, the organization of which on the HOPG substrate was found to be structure-specific. Electrical/electronic properties of the three carbo-mers were determined by using Atomic Force Microscopy (AFM) and its electrical modes: Kelvin Probe Force Microscopy (KPFM) and conductive Atomic Force Microscopy (c-AFM). Measurements of the work function (∅) through KPFM result in a ∅ = 5.60 eV value for 1, 4.97 eV for 2 and 4.82 eV for 3. Hole mobility (µ) values extracted from local I-V plots by using c-AFM are 15×10−8cm2V−1s−1 for 1, 3×10−6cm2V−1s−1 for 2 and 87×10−8cm2V−1s−1 for 3. A concept test of the possible application of carbo-mers in self-assembled hole transporting monolayer (SA-HTM), with the view to replacing the most common p-type contact used in organic solar cells (OSCs), PEDOT:PSS, is also reported.

Temperature induced supramolecular structural transition and as a host cavity to capture the guest molecules

The two-dimensional (2D) molecular self-assembled arrangements at the liquid–solid interface are dominated by many parameters such as the molecular structure and the environment of adsorbed molecules. In this study, the impact of temperature on the self-assembled structures of tetrathiafulvalene derivatives TTF-C6, which contains two aromatic carboxyl groups and two alkyl side chains, was investigated by scanning tunneling microscopy (STM) technique. Experimental result reveals that the compacted linear structures of TTF-C6 can be transformed into the cavity structures by increasing the HOPG substrate temperature. The cavity structures can serve as template system to capture different guest molecules such as coronene (COR) and C60. However, the proportion of two guest molecules in the host cavities is different. The corresponding density functional theory (DFT) calculations were carried out to verify the experimental results. Such temperature-induced structural transitions are used to adjust the packing density of molecule and capture different guest molecule.

The Electronic State of Pt Nanoparticles on an Ion-Beam-Irradiated Carbon Support

Pt nanoparticle electrocatalysts on an Ar+-irradiated glassy carbon (GC) substrate were recently found to show a higher oxygen reduction reaction (ORR) activity than those on the non-irradiated one [1]. This finding suggests that the Pt nanoparticles would be electronically modified by the lattice defects in irradiated GC. Our theoretical research previously revealed that vacancies in graphite would lower a d-band center of the supported Pt nanoparticles; this is probably the reason for the higher activity [2]. We investigated here the electronic states of the interface between the Pt nanoparticles and the irradiated carbon support by X-ray absorption fine structure (XAFS) measurements in order to get an insight into the mechanism of the activity enhancement.Highly oriented pyrolytic graphite (HOPG) and glassy carbon (GC) substrates were irradiated with 380 keV Ar+. The HOPG substrate was employed so that the electronic structure could be resolved into orbital components (σ and π bonds). The Pt nanoparticles were then deposited by RF magnetron sputtering. The Pt deposition was also done on the non-irradiated HOPG and GC substrates for comparison. The XAFS spectra were measured at BL14B1 in SPring-8 and at BL-8 of the SR Center, Ritsumeikan University.Figure 1 shows the C-K XAFS spectra for the pristine HOPG, the irradiated HOPG, Pt/non-irradiated HOPG, and Pt/irradiated HOPG. This spectral measurement was made at the X-ray incident angle of 30° to obtain the X-ray absorption due to C-C π* and s* orbitals with almost the same cross-section. The pristine and irradiated HOPG substrates exhibited three peaks from a C-C π* orbital (285.3 eV), C-C σ*, σ1 orbital (291.5 and 292.5 eV), and surface carbon with adsorbates (287.5 eV). The shoulder structure around 284 eV was observed for Pt/non-irradiated HOPG, indicating the occurrence of Pt-C interaction at the interface. The intensity of this shoulder increases for Pt/irradiated HOPG as shown by the arrow. Therefore, the vacancies in the irradiated carbon support would induce the change of Pt-C interaction, leading to the different electronic structure at the interface.Our previous paper reported that the Pt nanoparticles on the irradiated carbon support were distorted [3]. According to the result of Fig. 1, the Pt-C interaction could be an origin of the observed distortion of the Pt nanoparticles, which lowered the d band center and then improved their ORR activity. In this presentation, we will additionally clarify the electronic structure of Pt nanoparticles based on the XAFS results of Pt L edge.

Interactions of Ti and its oxides with selected surfaces: Si(100), HOPG(0001) and graphene/4H-SiC(0001)

The paper presents an interaction of Ti/Ti-oxides with: Si(100), HOPG(0001) and graphene/4H-SiC(0001) substrates. A thin layer (~3 nm) of Ti was deposited by means of DC sputtering technique on all the considered substrates. XPS, AFM and Raman spectroscopy were applied to find out the differences in interaction of Ti/Ti-oxides with selected substrates under UHV annealing. In the case of Si(100), substrate, apart from the expected TiO2, the presence of TiSi2 and TiSiOx components and the easiest reduction towards Ti2O3 was observed under UHV annealing. The sample exhibited also substantial evolution of surface morphology without the change of surface roughness which was attributed to formation of TiSi2 and TiSiOx components. This was in contrast with HOPG substrate where an annealing-induced agglomeration of the deposited material increased the surface roughness substantially. However, in the case of Ti/Ti-oxides deposited on graphene/4H-SiC(0001), UHV annealing caused no noticeable change of surface morphology. Agglomerates were not formed which was attributed to degradation of graphene (confirmed by Raman spectra) and supressing van der Waals' interactions responsible for easy surface diffusion. The differences in morphology were also discussed in the context of the surface energy of selected substrates.

(Invited) Monolayer h-BN: Epitaxy, Properties, and Emerging Device Applications

Hexagonal boron nitride (h-BN) has shown tremendous promise when used alongside other two-dimensional (2D) materials such as graphene, and as a wide-bandgap semiconductor for deep-ultraviolet optoelectronics and quantum photonics. Owing to its large bandgap energy comparable or higher than Al(Ga)N, h-BN can be used to form heterostructures to address some of the critical challenges of Al(Ga)N-based systems. To date, however, many fundamental material properties of h-BN remain unknown. For example, its bandgap energy remains under debate, with reports spanning from 5.9 to 6.5 eV. There is also strong controversy as to whether h-BN has a direct or indirect bandgap. In this context, We have studied the epitaxy of h-BN by using ultrahigh temperature (up to 1850 °C) plasma-assisted molecular beam epitaxy (MBE) on sapphire, Ni and HOPG substrates. We show that, when grown at sufficiently high temperature, h-BN can exhibit predominantly excitonic emission at ~220 nm. The measured luminescence intensity is orders of magnitude higher than AlN under identical conditions. By forming a p-i-n structure using this high-quality h-BN as the active region, the current-voltage (I-V) and electroluminescence characteristics of a first demonstration of a h-BN deep UV LED will be reported.

Electrochemical Study of Li-Ion Battery Anode (Graphite) and Cathode (NMC811) Surface Film Formation By in-Situ Scanning Probe Microscopy

Lithium ion battery usage has grown significantly in recent years. To obtain the best from the li-ion battery technology, it is important to understand both advantages and the limitations from the fundamental point of view. In lithium-ion batteries, layer structured graphite is the most commonly used anode material and NMC is one of the modern choices of cathode materials for high capacity Li-ion batteries in the electric vehicle applications [1,2,3].During the first charging process, the electrochemical reduction of electrolyte components gets deposited on the surface of anode resulting solid electrolyte interface (SEI) layer formation [4,5,6]. It is widely accepted that the batteries benefit from a proper SEI formation, as it can improve their lifetime, cycle life, power capability and safety [7].Morphological structure of SEI layer formed on HOPG and cathode electrolyte interface (CEI) layer formed on NMC plays an important role in lithium-ion battery (LIB), particularly for its cyclability and safety. For the development of high-performance LIB’s, it is crucial to understand the SEI layer formation on anode side [8] and the less studied corresponding layer formed on cathode side termed as CEI, whose composition and role are debated [9].Microscopic techniques, which include scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are the most powerful tools to measure the electric current and surface topography [10,11]. Within this work, we present in-situ electrochemical atomic force microscopic (EC-AFM) studies of surface reaction and topographic evolution of SEI and CEI layers formed on HOPG and NMC811 substrates. EC-AFM morphological analysis is also complemented with XPS (X-ray Photoemission Spectroscopy) characterisation for elemental composition, which brings a new insight in the comparison of SEI/CEI decomposition products. Acknowledgements: This work is partially supported by Faraday Institution (EP/S003053/1) and North-East Centre of Energy Materials-NECEM (EP/R021503/1) funded by EPSRC.

Preparation and characterization of CdSe/POMA photoactive composites electrochemically grown on HOPG surfaces

Visible light driven photoactive inorganic-organic hybrid composites were prepared containing cadmium selenide (CdSe) and poly(o-methoxyaniline) nanofilms. The films were fabricated in three different configurations: i. Composite of CdSe deposited onto HOPG with o-methoxyaniline (POMA) deposited on top (HOPG/CdSe/POMA), ii. Composite of POMA deposited onto the HOPG substrate with CdSe deposited on top (HOPG/POMA/CdSe), iii. Composite made through the simultaneous deposition of CdSe and POMA (HOPG/(CdSe/POMA)) on HOPG substrate. The photoactivity and physico-chemical properties of the fabricated composites were examined through electrochemical, XPS, Raman, in situ AFM and STS techniques. The changes in morphology, optical, spectroscopic, photoactive properties and elemental composition of the hybrids were monitored depending on the composite design, namely: number of the deposition cycles or order of component deposition. The HOPG/CdSe/POMA was identified as the most photoactive and stable composite and hence this material was further examined for its properties. In all cases of the fabricated hybrids, n-type and p-type photocurrents were observed. As the thickness of POMA increases, the p-type photocurrent decreases, while the n-type photocurrent increases. It is proposed that the p-type photocurrent observed is due to the presence of elemental selenium. The n-type photocurrent is attributed to CdSe layer. The amount of the polymer was optimized in order to maximize the photoactivity of the fabricated composite. The optimal POMA thickness, prepared in 5 deposition cycles, was determined by the AFM scratching technique to be 150 nm prepared. The highest photocurrent (224 μAcm−2) and highest photopotential (230 mV) were observed for the composite deposited on HOPG substrate with 20 deposition cycles of CdSe and 5 deposition cycles of POMA. The bandgap of the HOPG/CdSe/POMA composite was determined by the STS technique to be 2.2 eV.

FeCl2 monolayer on HOPG: art of growth and momentum filtering effect.

Magnetic layered transition metal halides have received intensive attention due to the potential magnetic properties in their monolayers. Following the recently reported success of trihalide monolayer ferromagnets, we have achieved the growth of a dihalide, FeCl2, monolayer system on graphite by molecular beam epitaxy. Scanning tunneling microscopy was used in the topographic and spectroscopic study of the monolayer islands at the atomic scale. Results show that the FeCl2 monolayer is an electronvolt-gaped insulator with various twist angles relative to the substrate. The tunneling probability on the monolayer islands is a function of the twist angle with a max/min ratio of ∼2.5. Our direct experimental evidence finds that the FeCl2 monolayer is an efficient momentum, perhaps spin, filtering insulating layer with subnanometer thickness.

Martensitic transformation in free-standing Cu-Al-Ni thin films with micrometric grain size

The martensitic transformation of polycrystalline thin films based on shape memory alloys is usually affected by the average grain size and by the thickness. We have carried out a study of the temperature driven martensitic transformation in micrometric grain size Cu-Al-Ni films with 18R structure. Thin films with a thickness of 6 μm were grown by sputtering on highly oriented pyrolytic graphite HOPG (0001) substrate at 873 K. After that, the samples were peeled-off from the substrate and annealed at 1123 K for 30 min. The observed microstructure shows an average grain size of 3.7 (± 0.2) μm. The martensitic start temperature (Ms) for different films ranges from 170 K to 370 K due to small changes in the chemical concentration. The influence of surface oxides and changes in the atomic order produced by post-quench aging treatments is analyzed. The results show that while surface passivation has a weak influence, changes in the atomic order increase Ms without impacting significantly on the hysteresis. Comparison with previous results of nanometric and micrometric grain size samples reveals that the barriers for the transformation are mainly given by plastic deformation at grain boundaries.

Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces

AbstractThermal desorption experiments of Formamide (NH2CHO) and methylamine (CH3NH2) were performed in LERMA-Cergy laboratory to determine the values of the desorption energies of formamide and methylamine from analogues of interstellar dust grain surfaces, and to understand their interaction with water ice. We found that more than 95 % of solid NH2CHO diffuses through the np-ASW ice surface towards the graphitic substrate, and is released into the gas phase with a desorption energy distribution Edes = (7460 – 9380) K, measured with the best-fit pre-exponential factor A=1018 s-1. Whereas, the desorption energy distribution of methylamine from the np-ASW ice surface (Edes =3850-8420 K) is measured with the best-fit pre-exponential factor A=1012s-1. A fraction of solid methylamine, of about 0.15 monolayer diffuses through the water ice surface towards the HOPG substrate, and desorbs later, with higher binding energies (5050-8420 K), which exceed that of the crystalline water ice (Edes =4930 K), calculated with the same pre-exponential factor A=1012 s-1.

Polymorphic self-assembly of pyrazine-based tectons at the solution-solid interface.

Exploring the surface self-assembly of small molecules that act as building blocks (tectons) for complex supramolecular structures is crucial for realizing surface-supported functional molecular devices. Here, we report on the synthesis and surface self-assembly of a new pyrazine-derived molecule with pyridine pendants. Ambient scanning tunneling microscopy investigation at the solution–solid interface reveals polymorphic self-assembly of these molecules on a HOPG substrate. Two different molecular packing structures with equal distribution are observed. Detailed analysis of the STM images emphasizes the crucial role of weak intermolecular hydrogen bonding, and molecule–substrate interactions in the formation of the observed polymorphs. Such weak hydrogen bonding interactions are highly desirable for the formation of modular supramolecular architectures since they can provide sufficiently robust molecular structures and also facilitate error correction.

Cooperativity and coverage dependent molecular desorption in self-assembled monolayers: computational case study with coronene on Au(111) and HOPG.

One of the common practices in the literature of molecular desorption is the comparison of theoretically (mostly using DFT) calculated single molecule adsorption energies with experimental desorption energies from studies like temperature programmed desorption (TPD) etc. Comparisons like those do not consider that the experimental desorption energies are obtained via ensemble techniques while theoretical values are calculated at the single molecule level. Theoretical values are generally based upon desorption of a single molecule from a clean surface, or upon desorption of an entire monolayer. On the other hand, coverage dependent molecule-molecule interactions add to and modify molecule-substrate interactions that contribute to the experimentally determined desorption energies. In this work, we explore the suitability of an additive nearest neighbor model for determining general coverage dependent single molecule desorption energies in non-covalent self-assembled monolayers (SAMs). These coverage dependent values serve as essential input to any model attempting to reproduce coverage dependent desorption or for understanding the time dependent desorption from a partially covered surface. This method is tested using a case study of coronene adsorbed on Au(111) and HOPG substrates with periodic DFT calculations. Calculations show that coronene exhibits coverage and substrate dependence in molecular desorption. We found that intermolecular contact energies in the coronene monolayer are not strongly influenced by the HOPG substrate, while coronene desorption on Au(111) exhibits strong cooperativity where the additive model fails.

Bio-Memristor Based on Peptide and Peptide Composite with Gold Nanoparticles

The structure, morphology and electrical properties of thin dipeptide hexamethylenediamide bis (N-monosuccinylglutamlysin) (DPT) layers and a DPT composite with gold nanoparticles deposited on gold and HOPG substrates were studied by probe microscopy and spectroscopy. The chemical formula of DPT is: {HOOC–(CH2)2–CO-L-Glu-L-Lys-NH–(CH2)3}2, and it is a mimetic of nerve growth factor. The results demonstrate that the structure and morphology of DPT thin layers depend significantly on the molecule charge (neutral or anion) and the nature of the substrate–layer interface. It was possible to control the structure and properties of the formed solid layers by changing pH of aqua solution (the charge of the DPT molecule). Bipolar resistive switching was observed in thin DPT layers on graphite and gold surfaces. The crystallization of anions on the surface of gold led to the formation of a ferroelectric unlike graphite. A strong dependence of the morphology of DPT composite layers on the nature of the substrate and the state of its surface is revealed. It indicates the important role of interfacial interactions in the crystallization processes of the DPT layers. The electrical properties of layers also depend on the interaction of DPT with the substrate. An increase in the thickness of the layers significantly affects the morphology and value of the tunneling current. Similar to crystallization of DPT salt on a gold surface, crystallization of DPT composite with gold nanoparticles also leads to the formation of a ferroelectric. The differences found in the structure of DPT composite layers on graphite and gold surfaces can be explained by assuming that the structure of the second and all subsequent layers is completely determined by the structure of the first adsorption layer in DPT-substrate interface. So this layer serves as a template for the growth of all other layers. The results can find practical application in 3D printing technologies. The presence of negative differential conductivity on local tunnel current–voltage characteristics of peptide composites is of great practical importance when used as active elements for amplifying current and power, memory cells in organic electronics. Investigated DPT has rather good memristive characteristics, including good endurance, satisfying ON/OFF current ratio, long retention time and reproducible write-once read-many times (WORM) memory behavior. All this allows us to consider the DPT to be a perspective material of memristor organic electronics. Since it is also a drug, the polymorphism and its dependence on pH can also find application in the pharmaceutical industry.