# US 10,319,553 B2 · Method for controllably growing ZnO Nanowires > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,319,553 B2 - Document ID: US10319553B2 - Status: Granted - Kind: B2 - Application number: 16/084,433 - Filed: 2017-03-14 - Published: 2019-03-14 - Granted: 2019-06-11 - Earliest claimed: 2016-03-16 - Assignees: Lightlab Sweden AB - Applicants: Lightlab Sweden AB - Inventors: Jonas Tirén; Jan-Otto Carlsson; Helena Tenerz; Patrik Hollman - Web page: https://patentgrep.com/patent/US10319553B2 ## CPC - H01J 9/025: {of field emission cathodes} - H10P 14/203: {using transformation of metal, e.g. oxidation or nitridation} - H10P 14/3426: {Oxides} - H10P 14/3462: {Nanowires} - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - H01J 63/06: Lamps with luminescent screen excited by the ray or stream - H01J 2201/30415: needle shaped - H01J 2201/30446: characterised by the emitter material - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES ## Abstract The present invention relates to a method for controllably growing ZnO nanowires, for example to be used in relation to field emission lighting. In particular, the invention relates to a method of controlling thermal oxidation conditions to achieve steady-state conditions between an oxygen consumption rate by a growing oxide on a surface of a structure and the decomposition rate of the oxygen-carrying species within the chamber. The invention also relates to a corresponding field emission cathode. ## Claims ### Claim 1 A method for controllably growing zinc oxide (ZnO) nanowires on a surface of a structure by means of thermal oxidation, the structure comprising a zinc layer covering at least a portion of the structure, the method comprising: arranging the structure within a thermal oxidation chamber, the chamber having a gas inlet and a gas outlet for allowing a gas flow through the chamber; providing a gas comprising an oxygen-carrying precursor through the gas inlet of the chamber; and controlling a concentration of oxygen along the surface of the structure by: controlling a temperature within the chamber; and controlling a gas flow of the gas comprising the oxygen-carrying precursor through the chamber, such that steady-state conditions are achieved between an oxygen consumption rate by a growing oxide on the surface of the structure and the decomposition rate of the oxygen-carrying species within the chamber, thereby maintaining the same zinc oxidation conditions along the surface of the structure within the chamber. ### Claim 2 (depends on 1) The method according to claim 1, wherein said gas comprises a plurality of oxygen carrying precursors. ### Claim 3 (depends on 1) The method according to claim 1, further comprising controlling a gas pressure to provide substantially uniform growth conditions at the entire surface of the structure, at a given time. ### Claim 4 (depends on 1) The method according to claim 1, further comprising controlling the gas flow such that a resulting concentration of oxygen is substantially uniform for the entire surface of the structure. ### Claim 5 (depends on 1) The method according to claim 1, wherein the oxygen-carrying precursor is selected from a group comprising of O2, CO2, N2O and H2O. ### Claim 6 (depends on 1) The method according to claim 1, further comprising selecting a concentration of the oxygen precursor of the gas provided to the chamber. ### Claim 7 (depends on 1) The method according to claim 1, wherein the gas is a gas mixture further comprising at least one of nitrogen and argon. ### Claim 8 (depends on 1) The method according to claim 1, wherein the temperature is controlled according to a predetermined temperature curve. ### Claim 9 (depends on 8) The method according to claim 8, wherein the temperature curve is selected based on a decomposition rate of the oxygen-carrying precursor. ### Claim 10 (depends on 8) The method according to claim 8, wherein the temperature curve comprises ramping up the temperature to an oxidation temperature using a fixed ramp, maintaining the oxidation temperature for a predetermined time, and ramping down the temperature using a fixed ramp. ### Claim 11 (depends on 8) The method according to claim 8, wherein the temperature curve comprises: ramping up the temperature to a first oxidation temperature using a first ramp rate; performing thermal oxidation starting at the first oxidation temperature for a first period of time to form an initial oxide layer; ramping up the temperature to a second oxidation temperature using a second ramp rate; performing thermal oxidation at the second oxidation temperature for a predetermined period of time to initialize and to maintain nanowire growth; ramping up the temperature to a third oxidation temperature using a third ramp rate and performing thermal oxidation during the temperature ramp to grow nanowires; and when the third oxidation temperature is reached, ramping down the temperature to end the oxidation using a fourth ramp rate. ### Claim 12 (depends on 11) The method according to claim 11, further comprising, when the third oxidation temperature is reached, ramping the temperature up or down to a fourth temperature using a fourth temperature ramp, and maintaining the fourth temperature for a predetermined period of time, before ramping down the temperature to end the oxidation using a fifth ramp rate. ### Claim 13 (depends on 1) The method according to claim 1, wherein the third oxidation temperature within the chamber is equal to or lower than 625° C. ### Claim 14 (depends on 1) The method according to claim 1, wherein a pressure within the chamber is a maximum of 1 atm. ### Claim 15 (depends on 1) The method according to claim 1, further comprising: preparing the structure by applying a predetermined thickness of a ZnO layer to the surface of the structure. ### Claim 16 (depends on 1) The method according to claim 1, wherein the structure comprises at least one of copper and brass. ### Claim 17 (depends on 1) The method according to claim 1, wherein the structure comprises a wire, a mesh or a plate. ### Claim 18 (depends on 1) The method according to claim 1, wherein a length of the ZnO nanowires is selected to be between 2-100 um. ### Claim 19 (depends on 1) The method according to claim 1, wherein a diameter of the ZnO nanowires is selected to be between 5-100 nm. ### Claim 20 (depends on 1) A field emission light source comprising a structure provided with ZnO nanowires grown according to claim 1. ### Claim 21 (depends on 19) The field emission light source according to claim 19, wherein the field emission light source is a UV light source.