High Quality Diamond Research Articles

Mapping sensitivity of CVD diamond detector using synchrotron micro-beam

In this project, we conducted micro-beam sensitivity mapping using the Diamond Light Source (DLS) synchrotron. We fabricated three samples with distinct metal contacts: Platinum (HPS-Pt) and Aluminium/Platinum (HPS-Al/Pt) on high-quality single crystal CVD diamond, and Platinum (VS-Pt) on lower purity single crystal CVD diamond. Our objective was to identify the most suitable sample for synchrotron measurements, particularly focusing on the lower purity sample due to its unique characteristics, such as thin nitrogen lines and substrate area.High spatial resolution sensitivity maps were obtained for the lower purity sample using a micro step displacement of up to 10 μm, revealing detailed nitrogen lines. We observed that bias polarity significantly influenced the photocurrent, with negative bias yielding higher photocurrents, possibly due to polarisation effects. Near nitrogen lines, we noted a slow rise time and an increased stabilization time with bias, alongside a prolonged decay to dark current.For the HPS-Al/Pt sample, we found no improvement in current response homogeneity, therefore reliability, with bias; instead, we recorded high dark currents and unstable signals, particularly at negative bias. Conversely, the HPS-Pt sample exhibited a uniform response at both +50V and −50V in the central region of the sensitivity maps. This response became increasingly homogeneous at 100V and further improved up to 200V, suggesting that HPS-Pt is the most suitable candidate for synchrotron measurements.

Growth of homoepitaxial single crystal diamond by microwave plasma CVD in H2-CH4-O2 gas mixtures at high microwave power densities

Single crystal diamond growth by microwave plasma assisted CVD in oxygen-containing gas mixtures is attractive in view of possibility to realize a prolonged non-stoped synthesis process and to minimize defects and impurities in the produced material. We studied the homoepitaxial diamond growth on (100) oriented substrates in H2-CH4-O2 environment at high pressures (300 Torr) and high microwave power density (≈400 W/cm3) at variable O2 content (up to 3.5 %) in the plasma. A low-coherence optical interferometry and optical emission (OE) spectroscopy was used to measure in situ the growth rate and probe the plasma chemistry, respectively. Depending on CH4 content the growth rate dependence on the concentration [O2] either shows a maximum at certain [O2], or a monotonic decline, up to complete stop of the growth at some critical O2 percentage (specific for each methane content) in the mixture. We found CH, Hβ, C2 and C3 lines in OE spectra from the plasma to monotonically quenched with O2 adding, particularly, disappearance of the C2 line coincidences with growth rate going to zero. High-quality homoepitaxial diamond layers were produced at moderate growth rate at optimal gas composition and characterized with Raman spectroscopy. Moreover, a significant reduction in the stress on (111) oriented substrates owing to O2 addition was observed.

MONOCRYSTALLINE DIAMOND MEMBRANES WITH A THICKNESS OF 10 MICRONS, MANUFACTURED BY PLASMA ETCHING

New applications of high-quality synthetic diamond in sensors and integrated photonic circuits, which are being rapidly developed nowdays, often demand freestanding diamond membranes with a thickness of about 10 microns as a substrate. However, the process of thin single-crystal diamond membranes fabrication, as well as their subsequent processing are challenging due to the high hardness, chemical resistance and brittleness of the material. Our work demonstrates a method for creating freestanding diamond membranes mounted on a thick diamond substrate using reactive ion etching of single-crystalline diamond wafers in plasma with mechanical protective masks. The optimal thickness of a diamond wafer for membranes etching is determined in the range from 100 to 120 µm with mandatory plane-parallel polishing of the sides. We experimentally studied the interaction of RF discharge SF6 based plasma with diamond surface during deep etching with mechanical protective masks of various shapes. It was found that the use of thick masks leads to an uneven rate of diamond etching over the entire area of the formed membrane. We have assessed ion sputtering resistance of various mask materials in SF6 based plasma, and found the most promising mask materials for deep diamond etching (steel, copper, diamond). We have fabricated diamond membranes with a thickness of 11,5 µm (and more), mounted on a durable 60 µm (and more) thick frames, and studied their characteristics. After etching membrane surface roughness was less than 25 nm, and the unevenness of their thickness did not exceed 20%. Also, we compare different methods for controlling the depth of diamond etching and the thickness of the resulting membranes, including mechanical measurements, IR spectral reflectometry, optical profilometry and electron microscopy. For citation: Golovanov A.V., Yun M.I., Bondarenko M.G., Prosin A.A., Tarelkin S.A. Monocrystalline diamond membranes with a thickness of 10 microns, manufactured by plasma etching. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 55-64. DOI: 10.6060/ivkkt.20246710.1y.

Pure Hexagonal Diamond with Symmetry-Doping Properties.

The difficulties in asymmetrical doping of wide band gap materials, especially for the n-type diamond challenge, hamper their application in electronic devices. Here, we propose doping diamond polytypes with reasonable band structures to solve this problem. Various elements are doped into six diamond polytypes, and their doping behaviors are investigated. The results show that pure hexagonal (2H) diamond has the band gap with a value of 4.42 eV and the smallest carrier effective masses among six calculated diamond polytypes, exhibiting high electron mobility and hole mobility up to 4250 and 5840 cm2·V-1·s-1, respectively. Compared to cubic (3C) diamond, the impurity formation energy in 2H-diamond is reduced, which is attributed to its C3v symmetry. More importantly, 2H-diamond exhibits favorable doping symmetry with a donor level of 0.14 eV for phosphorus and an acceptor level of 0.19 eV for boron, respectively, which originate from smaller effective masses and stronger delocalization at the band edge in 2H-diamond. These ionization energies are smaller than those in 3C-diamond of 0.32 and 0.58 eV, respectively. This reveals that phosphorus and boron in 2H-diamond are more easily excited at room temperature, producing good n- and p-type conductivities. All of these make 2H-diamond a potential candidate for the replacement of 3C-diamond as a wide band gap material theoretically. These provide a way to realize high-quality n-type diamond, giving significant insights into the realization of diamond-based electronic devices. This also supplies a solution for the difficulties in asymmetric doping of other wide band gap materials.

Oxygen-termination effect on the surface energy dissipation in diamond MEMS

Single-crystal diamond (SCD) microelectromechanical systems (MEMS) resonators with lower energy dissipation and higher quality (Q) factors have always been pursued for the development of high-sensitivity and high signal-to-noise ratio (SNR) MEMS sensors. The intrinsic loss such as the crystal quality and extrinsic loss of clamping loss have been examined to improve the Q factors of SCD MEMS resonators. Nevertheless, the surface termination induced energy dissipation has rarely been known due to the lack of high crystal quality diamond resonators and in-situ characterization. Here we examine the effect of oxygen-termination on the surface energy dissipation of SCD cantilevers by in-situ heating these cantilevers in a high vacuum chamber. After thermal treatment of the cantilevers at 933 K, the Q factor of the cantilever is improved from 2.8x105 to 3.3x105 (i.e. the 120 μm-long). The resonance frequency increase confirms the desorption of surface adsorbates. Compared to silicon, on which a native solid-state oxide exists, the surface oxygen-termination induced loss in diamond MEMS is much smaller. The non-existence of native oxides on diamond surface is an obvious merit toward ultra-high Q factor MEMS resonators.

Low-Temperature Deposition of Diamond Films by MPCVD with Graphite Paste Additive

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses these properties and is recently recognized as a promising dielectric material for the fabrication of advanced ICs, which are sensitive to detrimental high-temperature processes. Therefore, a high-rate low-temperature deposition technique for large-grain, high-quality diamond films of the thickness of a few tens to a few hundred nanometers is desirable. The diamond growth rate by microwave plasma chemical vapor deposition (MPCVD) decreases rapidly with lowering substrate temperature. In addition, the thermal conductivity of non-diamond carbon is much lower than that of diamond. Furthermore, a small-grain diamond film suffers from poor thermal conductivity due to frequent phonon scattering at grain boundaries. This paper reports a novel MPCVD process aiming at high growth rate, large grain size, and high sp3/sp2 ratio for diamond films deposited on silicon. Graphite paste containing nanoscale graphite and oxy-hydrocarbon binder and solvent vaporizes and mixes with gas feeds of hydrogen, methane, and carbon dioxide to form plasma. Rapid diamond growth of diamond seeds at 450 °C by the plasma results in large-grained diamond films on silicon at a high deposition rate of 200 nm/h.

Study on the synergistic mechanism of N[sbnd]H[sbnd]S[sbnd]O co-doping in diamonds

Nitrogen impurity remains a crucial focus in diamond impurity research. To address difficulties associated with excessive nitrogen impurities during the synthesis of high-quality diamonds under high-pressure and high-temperature conditions and to increase the proportion of aggregated nitrogen impurities in diamonds, we explored the multi-element growth environment of natural diamonds. In this study, we used N–H–S–O multi-component co-doping to increase the proportion of aggregated nitrogen impurities in diamond. Through Fourier-transform infrared spectroscopy characterization, we successfully used the synergistic mechanism of N–H–S–O co-doping to achieve a 47.9% proportion of aggregated nitrogen impurities in diamond in a single synthesis and successfully synthesized the type IaA + Ib diamond. Raman tests revealed a lower residual stress in the high-quality large single-crystal diamond synthesized. Moreover, we comprehensively analyzed the mechanism of N–H–S–O co-doping to increase the proportion of nitrogen impurities in diamond aggregates and proposed an optimal ratio principle based on the experimental results. This study presents a method for synthesizing diamonds with a high proportion of aggregated nitrogen impurities and provides valuable guidance for elucidating the origin of natural diamonds and synthesizing multi-doped functional diamonds.

Explore the growth mechanism of high-quality diamond under high average power density in the MPCVD reactor

Investigating the mechanism behind the high-efficiency deposition of high-quality diamond has always been a prominent topic in related research. This paper investigates the CH4-H2 plasma characteristics and related chemical reaction kinetics in the average power density range of 18–100 W·cm−3, which is a typical range for large-area diamond film deposition. The number densities of H, CH3 and C2H2 increase linearly with the average power density. C2H2 is the main hydrocarbon in the discharge, and CH3 is the main single-carbon hydrocarbon. The number density and radial uniformity of CH3 and C2H2 increase with the average power density, which is necessary for the high rate and uniform deposition of diamond films. The plasma's optical emission spectra indicate an acceleration in the C2 production rate at high power density. The diamond film deposition experiment demonstrates the efficacy of high average power density in achieving high-quality diamond deposition at a high growth rate.

Effect of Mechanically Created Pits Pattern for Direct Diamond Deposition on Stainless-Steel Surface

Direct diamond deposition on a steel surface has been considered very difficult. Recently, we found that high-quality diamond films can be deposited on the surface of stainless-steel X5CrNi 18-10 by drilling multiple regularly arranged pits without interlayers or seeding. The following two hypotheses (A) and (B) can be considered as the reason why a high-quality diamond film can be deposited: (A) unoxidized Cr and Ni exposed to the stainless-steel X5CrNi 18-10 surface prevent carbon diffusion into interior of the stainless-steel, resulting diamond core generation, (B) Surface geometry with regular roughness contributes to stress relaxation and delamination prevention. In the present study, those hypotheses have been examined by quantum chemistry calculation and experimental. For the quantum chemistry calculation, energy barrier and kinetic energy for a carbon atom intrudes into a model cluster has been calculated with an ab-initio computational chemistry software package, Gaussian. The calculation result has supported hypothesis (A). For the experiment, X5CrNi 18-10 stainless-steel substrates with different surface characteristics are prepared by using various mechanical machining methods and used in the direct deposition process for diamond with in-liquid plasma CVD. The experimental result has supported both hypothesis (A) and (B).

The synchronous detection technique for the accurate monitoring of high-energy pulsed X-rays

At high energy, the smaller inelastic nucleon-Carbon cross-section implies that diamond has a radiation hardness an order of magnitude higher than that of silicon. The production of high-quality diamond crystals and films grown using the chemical vapor deposition technique opened the way for the use of synthetic diamonds in the fabrication of detectors for charged particles and high-energy photons. More recently, laser-processing technology for the fabrication of three-dimensional contacts in diamond has been proposed to produce highly efficient detectors, even with ultra-low active volumes. However, buried-contact structures made with laser treatments unavoidably induce structural defects in the volume surrounding the buried columns, thus affecting the detector response due to trap-related charge transport mechanisms. When pulsed radiation is concerned, experimental results reported in this work demonstrate that synchronous signal conditioning can strongly mitigate the trap-mediated contribution, thereby improving the performance of the overall detection system. Significantly, these results pave the way for the application of diamond samples with three-dimensional buried-contacts in the development of detectors for accurate dosimetry.

Comparative of HPHT and CVD diamond: performance and defect analysis for alpha radiation detector

Currently, the high-purity single crystal diamond preparation is still a challenging task, which restricts the application of diamond in electronics. In this paper, the chemical vapor deposition (CVD) IIa type single crystal diamond was prepared on the IIa type high pressure high temperature (HPHT) substrate by combining the chamber design with the plasma purifying technology, and the performance of diamond detectors using both IIa type single crystal diamonds were compared based on the defect analysis. The dislocations in diamonds were directly observed by synchrotron radiation X-ray white-beam topography. The CVD diamond shows the comparatively low dislocation density resulting from the high-quality HPHT diamond substrate. No observable NV impurity could be found in photoluminescence (PL) spectrum. The trace impurity of substitutional nitrogen (Ns) was characterized by electron paramagnetic resonance (EPR). It shows the very low concentration in the CVD diamond (2.1 ppb) compared with the several tens ppb in HPHT diamond. This value is comparable with the electronic-grade diamond reported by Element Six. Furthermore, both of the HPHT and CVD single crystal diamonds were packaged as the α-particle radiation detectors with the typical sandwich structure and used Ni/Al (50 nm/500 nm) as metal electrodes. The energy resolution of HPHT and CVD diamond detectors were 2.04% and 0.86%, respectively. Based on Schottky contact and defect regulation, at 0 voltage, the CVD diamond detector achieved response of α-particle radiation and the charge collection efficiency (CCE) was 10.76%. Under positive voltage, the CCE of HPHT and CVD diamond detectors were 38.11% and 86.65%, respectively. The deep level trapping effect of Ns impurities on charge carriers resulted in low CCE of HPHT diamond detector. The spatial polarization effect caused by defects leaded to the formation of an internal electric field, which was the main reason affecting the transport of charge carriers in CVD diamond.

Effect of boron doping levels on the microstructure and characteristics of high-quality boron-doped diamond electrodes prepared by MPCVD

In order to fully understand the relationship between boron doping level and material characteristics, a series of high-quality boron-doped diamond (BDD) electrodes with different boron doping levels (B/C ratios = 1000–5000 ppm) were prepared on a silicon substrate using a self-designed microwave plasma chemical vapor deposition (MPCVD) reactor in this study. The relationship between surface morphology, structural composition, chemical bonding state, electrical conductivity and electrochemical properties of BDD electrodes was investigated systematically. With the increase of boron doping level, the grain size of the BDD electrode tends to decrease, the crystal orientation tends to be dominated by (111) orientation, the conductivity increases sharply and then gradually stabilizes, while the width of the potential window tends to decrease (4.39 V to 3.95 V from 1000 ppm to 5000 ppm), and the reversibility and stability of the electrode improves significantly. In addition, such high-quality BDD electrodes also exhibit a higher sensitivity (0.1176 μAμM−1 cm−2) and lower limit of detection (0.276 μM) in the detection of dopamine. The boron doping level in BDD electrodes plays a prominent role in material characteristics such as surface morphology, structural composition, chemical bonding state, electrical conductivity and electrochemical properties. Despite the challenging synthesis of pure sp3 carbon materials at high boron doping levels, the BDD electrodes prepared in this study exhibit high quality without sp2 defects even with high boron doping levels, and possess extremely low resistivity (~10−3 Ω·cm) and a wide electrochemical potential window (~4 V), which has not been achieved in other previous research works and offer great potential in the electrochemical applications of BDD electrodes.

Diamond growth in a high temperature and high pressure Fe–Ni–C–Si system: Effect of synthesis pressure

Pressure is one of the necessary conditions for diamond growth. Exploring the influence of pressure on growth changes in silicon-doped diamonds is of great value for the production of high-quality diamonds. This work reports the morphology, impurity content and crystal quality characteristics of silicon-doped diamond crystals synthesized under different pressures. Fourier transform infrared spectroscopy shows that with the increase of pressure, the nitrogen content in the C- center inside the diamond crystal decreases. X-ray photoelectron spectroscopy test results show the presence of silicon in the diamond crystals synthesized by adding silicon powder. Raman spectroscopy data shows that the increase in pressure in the Fe–Ni–C–Si system shifts the Raman peak of diamonds from 1331.18 cm−1 to 1331.25 cm−1, resulting in a decrease in internal stress in the crystal. The half-peak width decreased from 5.41 cm−1 to 5.26 cm−1, and the crystallinity of the silicon-doped diamond crystals improved, resulting in improved quality. This work provides valuable data that can provide a reference for the synthesis of high-quality silicon-doped diamonds.

H-Terminated Diamond MOSFETs on High-Quality Diamond Film Grown by MPCVD

Diamond-based transistors have been considered as one of the best choices due to the numerous advantages of diamond. However, difficulty in the growth and fabrication of diamond needs to be addressed. In this paper, high quality diamond film with an atomically flat surface was grown by microwave plasma chemical vapor deposition. High growth rate, as much as 7 μm/h, has been acquired without nitrogen doping, and the root mean square (RMS) of the surface roughness was reduced from 0.92 nm to 0.18 nm by using a pre-etched process. H-terminated diamond MOSFETs were fabricated on a high-quality epitaxial diamond layer, of which the saturated current density was enhanced. The hysteresis of the transfer curve and the shift of the threshold voltage were significantly reduced as well.

Diamond immersion photodetector for 213 nm deep-ultraviolet photodetection

Developing a photoelectric detector with independent power, compactness, and high environmental sensitivity is a key step to realize the energy-saving and sustainable integrated photoelectric system of next generation. In this paper, a p-type diamond single crystal (PDSC) is used as the photoelectrode to construct a self-powered deep ultraviolet light immersion photodetector with the photoelectrochemical (PEC) cell structure. Under the excitation of a deep ultraviolet light of 213 nm, this immersion photodetector exhibits an excellent responsivity of 20 mA W−1 and a short response/recovery time (50/38 ms). This superior performance is attributed to the successful synthesis of high-quality p-type diamond by the high-temperature and high-pressure method, which ensures an efficient light detection through the effective light collection. This kind of immersion detector based on the ultra-wide-bandgap diamond guarantees a stable detection for deep ultraviolet detection with efficient response, which displays a great potential in future application.

An innovative gas inlet design in a microwave plasma chemical vapor deposition chamber for high-quality, high-speed, and high-efficiency diamond growth

A novel design of the gas inlet system in a diamond microwave plasma chemical vapor deposition growth chamber has been reported in this paper. The design is targeting for high-quality, high-speed, and high-efficiency diamond material fabrication. By introducing a gas inlet hole into the susceptor, we expand the ways of gas introduction for diamond growth. After extensive numerical and experimental investigation, we have found that the introduction of methane and doping gas inlet from the hole of below while the hydrogen from the top is feasible for realizing the target. The growth and doping species could be confined around the substrate, making efficient usage of the precursors. The plasma state change caused by the difference of the gas inlet modes has been ascribed to the resulted gas distribution in the chamber. The measured growth rate has been increased to 32 μm h−1, which is 16 times higher than traditional gas inlet configuration. Meanwhile, a large improvement of the nitrogen doping concentration has been achieved. Besides, with the increase of growth rate and nitrogen incorporation efficiency, the crystal quality and surface morphology keep in an acceptable degree. In this mode, the dual gas flow system can perfectly solve the contradiction among the crystal quality, growth rate, and doping efficiency, commonly existing during the material fabrication process, the chamber contamination could be significantly suppressed due to the constrained distribution of methyl and doping species, making the fabrication cost much lower. The results of repetitive experiments indicate that other residual impurities present in the chamber of microwave plasma chemical vapor deposition could likely regulate the threshold concentration of nitrogen required for accelerating the growth rate during the nitrogen doped diamond growth, which have a significant effect on the diamond growth.

Вплив вибору марки ріжучих алмазів та концентрації УДПА у наповнювачі зв’язки на працездатність алмазних трубчастих свердл при обробці граніту та скла

The results of laboratory tests for drilling granite and window glass with diamond tube drills are given. The drills were made by the method of vacuum impregnation, developed at the Institute of Scientific Research of the National Academy of Sciences named after I. M. Frantsevich, and studied on a Sachsenwerk drilling machine (Dresden, Germany) in cold running water in order to prevent oxidation of diamonds and bonds due to their heating during work. The dependence of the efficiency of the drills on the content of very strong cutting diamonds of the AS500 500/400 brand, less strong — of the AS32 500/400 brand, as well as on the concentration of ultradispersed diamond powders (UDPA or ASM 1/0) in the filler of the tool bundles was studied. These indicators were compared with the indicators of drills equipped with diamond grains of the AS200 500/400 brand, which were obtained and described earlier when drilling the same non-metallic materials. The performance of diamond drills was evaluated by their wear and drilling speed. The highest quality tools can be obtained if you use high-strength diamond grains of the AS500 500/400 brand. The operational characteristics of such drills differed in high wear resistance (low wear) and drilling speed. The efficiency of drilling with diamond drills that were equipped with lower-quality diamond grains of the AS200 500/400 and AS32 500/400 brands was significantly lower. It was possible to increase the drilling speed and reduce the wear of such tools when the filler was introduced into the connection with ASM 1/0 in the amount of 5—7% (wt.) due to the improvement of its mechanical properties. But all the same, such diamond drills were inferior in efficiency to tools equipped with high-quality diamonds of the AS 500 500/400 brand. Keywords: diamond drills, bond samples, drilling tests, drilling speed, wear.

High-speed growth of high-quality polycrystalline diamond films by MPCVD

High-speed growth of high-quality polycrystalline diamond films by MPCVD

Influence of Diamond Seed Attachment Processing on Diamond Films Synthesized on Tungsten Carbide Substrate by Flame Combustion

The flame combustion method enables the synthesis of diamonds via acetylene-oxygen gas flame combustion in ambient air. Tungsten carbide (WC) has recently been utilized as a cutting tool in the machining industry and in dental machining applications. To obtain high-quality diamond films and achieve good adhesion on a WC substrate, diamond films are synthesized on a WC substrate by the flame combustion method. However, the surface roughness of most of the diamond films synthesized by this method increased, and it was necessary to reduce this roughness. Considering the roughness accuracy of the workpiece surface during cutting, and the performance of the cutting tool, a smaller surface roughness of the diamond films synthesized is desirable. In this study, to reduce surface roughness, the amount of diamond paste with diamond seed particles as generation nuclei was carefully varied for diamond seed attachment processing of diamond films. When diamond films were synthesized on the WC substrate surface via the flame combustion, the amount of diamond paste with diamond seed particles affected the surface morphology and surface roughness of the synthesized diamond films. Furthermore, to investigate the reason for this result, generation of nuclei on the substrate in the initial stages of synthesis and diamond seed particles on the substrate surface after the seeding treatment were observed by scanning electron microscopy. The effect of diamond seed attachment processing on the diamond films synthesized by flame combustion was studied. The relationship between the surface roughness, number of diamond generation nuclei on the substrate in the initial stages of synthesis, number of diamond particles on the substrate after the diamond seeding process, and amount of diamond paste were confirmed.

PLACER DEPOSITS OF DIAMONDS AND THEIR FORMATION CONDITIONS

This article reviews information from published papers and studies by the authors about placer diamond deposits. Original data were obtained in result of field and laboratory-analytical work carried out in various countries of Africa and South America. The main types of placer diamond deposits – fluvial, fluvioglacial, eolian, and man-made – have been considered and characterized. The main attention is given to fluvial continental placers, which are the most diverse, well-studied and have the greatest industrial importance. Primary, secondary and mixed deposits are distinguished according to the method of feeding; short, moderate and long transport deposits – according to the distance of the diamond-bearing material movement. It is noted that although the short transport placers (deluvial-proluvial and beds of short watercourses) have not industrial value, they are very informative for the searching for root sources. It is important to reliably diagnose these deposits by lithological-facies and mineralogical features during prospecting works. The concepts about the conditions for the formation of diamond placers in various landscape and geological conditions are developed and clarified. Alluvial-proluvial-lacustrine and proluvial-lacustrine types of placers studied in Yakutia and Brazil are characterized in detail. Their characteristic feature is that their productive strata, being re-deposited products of crustal weathering, themselves underwent a hypergenic change at the place of occurrence, which significantly masks the primary conditions of formation. Continental alluvial redeposition and long transport placers, as well as marine, yield the most high-quality expensive diamonds, the average value of which can reach $300–400 per carat. Often, such placers are formed due to the erosion of ancient Proterozoic placers, which belong to the category of fossils. The article summarizes the genetic and morphological types of diamond placers in the form of a principle diagram of the distribution of sedimentary reservoirs of kimberlite minerals. The landscape-dynamic zones of sedimentation are highlighted. A classification scheme of sedimentary reservoirs containing diamond placers has been developed. Continental, transitional and marine environments are distinguished, with further detalization of sedimentation environments – peneplain, alluvial-lacustrine accumulative plain, alluvial-deltaic plain and shelf zones of sea basins. It is shown that the formation of valley placers, their internal structure, thickness, granulometric composition and diamond content of alluvium are influenced by the dynamic phases of the formation of annual valleys. Visualization of the mutual relationship of different morpho-genetic types of placer diamond deposits is given.